Baked Leek Gratin

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If you’re like us, you’re always looking for a new side dish, especially during the holiday season. Look no further.

We make this dish for any occasion, but it is especially nice to serve for a holiday feast, such as Easter, Mother’s Day, or Passover. It matches perfectly against a slow-cooker spiral ham or roast leg of lamb. Our guests are always so impressed with this dish, and so will yours!

A close-up view of a partially eaten baked leeks gratin in a white and black oval baking dish with a large silver spoon inserted into the side of the dish.

How To Make Baked Leek Gratin

 

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The Ingredients You Will Need

Leeks are in their prime during the spring, which makes this dish perfect for an Easter menu, or Mother’s Day feast. Here’s what you’ll need to have on hand:

Butter – Unsalted
Shallots – Finely chopped. You can substitute chopped yellow onion, if necessary.
Leeks – Make sure you rinse them thoroughly under cool water to wash away any dirt hiding in the layers. Cut the white and some of the green parts into thin strips, and then roughly chop them.
Seasonings – Salt and pepper.
Milk – Whole is recommended. Half and half, or even heavy cream can be used, too.
Flour – All-purpose.
Cayenne pepper – For a little zip. For a little more spice, increase the cayenne amount, for no heat at all, simply omit it.
Cheese – Gruyére is highly recommended, but shredded white cheddar, fontina, or gouda would all be good choices, too.
Breadcrumbs – See NOTES.

EXPERT TIP: It will seem like you have a huge amount of leeks when you add them to your large skillet. They will cook down significantly after they sauté. This process can take about 15 to 20 minutes. They should be very soft.

A close-up view of a large silver skillet filled with strips of thinly sliced leeks being sautéed in butter and stirred with a wooden spatula.

Tips for Making Perfect Baked Leek Gratin

Select Fresh Leeks – Choose fresh, firm leeks with white and light green parts. Ensure they are thoroughly cleaned to remove any grit or dirt before using them in the gratin. Properly cleaned leeks will contribute to the overall quality and flavor of the dish.

Caramelize the Leeks – Take the time to properly caramelize the leeks to bring out their natural sweetness and depth of flavor. Sauté them slowly in butter or olive oil until they are soft and golden brown, which will enhance the overall taste of the gratin.

Use High-Quality Cheese – Opt for good-quality Gruyère cheese for its rich, nutty flavor and excellent melting properties. Grate the cheese fresh for the best results

Balance the Cream Mixture – The cream should be rich and flavorful without overwhelming the delicate taste of the leeks and Gruyère cheese. Be mindful of the balance to create a harmonious dish. Taste and adjust accordingly.

A person transferring sautéed strips of leeks from a large silver skillet into another skillet filled with béchamel sauce.

How to Serve

You’ll want the breadcrumb topping to brown lightly before removing from the oven. If you want the topping a little more browned and crunchy, turn the broiler on HIGH and allow the gratin to bake for another minute, or two. Keep an eye on it, however, and don’t let it burn!

This dish is very hot when it comes out of the oven. It should rest for at least 5 to 10 minutes. However, you can also cover it and let it rest for up to 30 minutes while you finish the rest of the dishes. It will stay warm.

Though this dish is best served shortly after being removed from the oven, leftovers are delicious, too.

EXPERT TIP: To make amazing breadcrumbs, set 1 to 2 slices of Italian bread out for a few hours to dry out. Use a sharp knife to remove the crusts and then process in your food processor until fine. Toss with melted butter and then top the gratin.

A person sprinkling buttery bread crumbs over the top of an uncooked leeks gratin in an oval baking dish.

Other Amazing Side Dish Recipes to Make and Serve

Sometimes side dishes can upstage the main course. Here are a few of our favorites that are sure to be a huge hit for your special feast:

Potatoes Dauphinoise (French au Gratin Potatoes)
Potatoes Fondant (Melting Potatoes)
Wild Rice, Spinach, and Fontina Casserole
Best-Ever Mashed Potatoes
Maple Glazed Carrots
Roasted Asparagus with Chopped Eggs
Asparagus Soufflé
Braised Green Beans with Tomatoes
Brussels Sprouts Gratin
Creamy Cauliflower Gratin
Cream of Corn Casserole
Stewed Tomatoes with Okra

These are absolutely amazing and a big hit whenever they are served. But, in the meantime, isn’t this dish calling your name?

An overhead view of an oval black and white baking dish filled with a fully cooked baked leeks gratin with lightly browned bread crumbs on top.

There is just so much to love with this creamy side dish.

It’s cheesy, creamy, loaded with flavor with a crunchy breadcrumb topping, and it’s something a little different!

If you’re looking for one more scrumptious side dish to round out your holiday feast, this is it! Your loved ones will thank you for it!

A close-up view of a large silver serving spoon lifting a helping of baked leeks gratin from a dish of the same.

Ready to make the best side dish in town? Go for it!

And when you do, be sure to take a photo of it, post it on Instagram, and tag @HowToFeedaLoon and hashtag #HowToFeedaLoon!

An overhead view of a baking dish filled with a baked leeks gratin with a portion of the casserole missing with a serving spoon in the side.

Baked Leek Gratin

This dish is the perfect side, especially for a "special occasion" feast such as Easter, Mother's Day, or even Sunday dinner. It may feel like you are starting with too many leeks, but, don't worry, they cook down fairly quickly. The dish can even be prepared almost completely in advance! (See Notes).
5 from 1 vote
Print Pin Rate
Course: Side Dish
Cuisine: American / French
Keyword: baked leeks recipe, how to cook with leeks, leeks gratin recipe
Prep Time: 20 minutes
Cook Time: 50 minutes
Resting Time: 10 minutes
Total Time: 1 hour 20 minutes
Servings: 6
Calories: 336kcal

Equipment

  • 1 1-quart baking dish smaller than a 9x13"

Ingredients

  • 8 tbsp unsalted butter divided
  • 5 to 6 leeks washed, sliced, and roughly chopped, use mostly the white parts and some of the green.
  • 1 large shallots chopped
  • Salt and pepper
  • 3 tbsp all-purpose flour
  • 2 cups whole milk
  • ½ tsp cayenne pepper
  • 1 tbsp lemon juice
  • 1 cup Gruyére cheese grated
  • cup fresh bread crumbs See NOTES

Instructions

  • Preheat oven to 400°F.
  • In a large skillet (12"), melt 3 tbsp butter over medium heat. Add the leeks and shallots, and cook, stirring often, until softened and starting to lightly brown, about 15 minutes. Stir in 1 tsp salt and ½ tsp black pepper.
    8 tbsp unsalted butter, 5 to 6 leeks, 1 large shallots, Salt and pepper
  • Either use a new skillet or transfer the sautéed leeks to a bowl and clean out the skillet with a damp paper towel.
  • Heat 3 tbsp butter over medium heat until melted. Whisk in the flour and stir until completely combined and cook, stirring often, for 1 minute.
    3 tbsp all-purpose flour
  • Whisk in the milk and stir until almost all lumps are no longer visible. Stir in the cayenne, lemon juice, ¾ tsp salt, and ½ tsp black pepper. Stir until thickened, about 3 to 4 minutes. The consistency should be like gravy, but not too thick.
    2 cups whole milk, ½ tsp cayenne pepper, 1 tbsp lemon juice
  • Turn off the heat and stir in the leek mixture. Stir until combined. Transfer to the baking dish and top with the grated cheese.
    1 cup Gruyére cheese
  • Toss the breadcrumbs with the remaining 2 tbsp butter (melted).
    ⅔ cup fresh bread crumbs
  • Bake until bubbly and slightly golden on top, about 25 to 30 minutes. Remove from oven and let rest for 5 to 10 minutes before serving. (Or, cover with foil, and let rest for up to 30 minutes).

Notes

See the video near the top of the blog post for visual guidance. If you liked the video, please subscribe to our YouTube channel. 
To make fresh breadcrumbs, place 1 to 2 pieces of bread (preferably Italian or French) out on the counter for several hours, or up to overnight. Use a sharp knife to cut off the crusts and then place the bread (torn into pieces) into your food processor and process until very fine. You can also process bread that is not dried out and you'll get a nice breadcrumb topping. It won't be quite as crunchy, but still delicious. Store-bought are perfectly fine, too. We prefer plain Panko, for the best texture. 
The gratin can be prepared up to 24 hours in advance. Just don't add the breadcrumbs until just before baking. Keep the unbaked dish covered in the fridge and let it sit out for about an hour before baking. 
Leftovers will keep refrigerated for up to 5 days. Reheat in the oven or in the microwave until heated through. 

Nutrition

Calories: 336kcal | Carbohydrates: 18g | Protein: 11g | Fat: 25g | Saturated Fat: 15g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 7g | Trans Fat: 1g | Cholesterol: 74mg | Sodium: 206mg | Potassium: 302mg | Fiber: 2g | Sugar: 7g | Vitamin A: 2113IU | Vitamin C: 10mg | Calcium: 373mg | Iron: 2mg
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3 Comments

  • 5 stars
    This was absolutely delicious!! My whole family loved it and devoured it all! Thank you so much for sharing the recipe!!

    • Hi Mimi! We completely agree! We knew we wanted to come up with something featuring leeks, and finally decided a gratin was be a yummy dish. And we think it’s really so good and a perfect holiday side dish. Happy Easter!!! xoxo

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