Heat 2 tablespoons of the oil in a large skillet over medium-high heat until shimmering.
3 tbsp olive oil
Add spinach and cook, stirring occasionally, until wilted, about 3 to 4 minutes.
16 oz fresh spinach
Transfer spinach to a colander and press with a large spoon to release excess liquid. Wipe out the skillet with a paper towel.
Pat chicken breasts dry with paper towels and then season with salt and pepper.
6 chicken breasts, Kosher salt and freshly ground black pepper
Heat the remaining 1 tablespoon of oil in the skillet over medium-high heat.
Add chicken and cook until browned, about 4 to 5 minutes per side.
Transfer the chicken to a clean platter or plate.
To the same skillet, add the shallot and cook for about 2 minutes, or until soft. (If the pan is dry, add a little more oil). Add the garlic and sauté for another 30 seconds.
1 shallot, 3 cloves garlic
Stir in stock and cream, scraping up any browned bits, and bring to a boil, then reduce heat to medium-low.
2 cups chicken stock, 1 cup heavy cream
Meanwhile, transfer the chicken to a cutting board and cut it into strips or bite-sized pieces. Add back into the sauce and simmer for 15 to 20 minutes, or until the sauce has reduced by about 1 cup.
Off heat, stir in the cooked spinach, ½ cup Parmesan, lemon zest, juice from half a lemon, ½ tsp salt, ½ tsp pepper, and the red pepper flakes.
¾ cup Parmesan cheese, 1 tsp lemon zest, 1 tsp fresh lemon juice, ½ ts red pepper flakes
Adjust oven rack to upper-middle position and heat broiler to HIGH.
Sprinkle the remaining ¼ cup Parmesan over the top of the chicken florentine.
Broil until golden brown, about 3 - 5 minutes, or less (keep a close eye, broilers vary!). Serve at once over cooked pasta or steamed rice.
8 oz pasta