Preheat the oven to 400°F and line 2 baking sheets with parchment paper. Use a 1½-inch cookie cutter to draw circles on the parchment paper about 1 to 2 inches apart. Flip the paper over, so the ink is on the underside of the paper.
Cook the bacon in a large skillet over medium heat until crisp. Transfer the bacon to a plate lined with paper towels, and save the rendered grease, about ¼ cup. Chop the bacon is cool (you should have about 1/2 cup).
4 strips thick-sliced bacon
Bring the milk, ½ cup water, the butter, and the reserved bacon grease to a simmer in a medium saucepan over medium heat.
½ cup whole milk, 4 tbsp unsalted butter
Mix in the salt, onion powder, sugar, cayenne, and oregano.
1 tsp Kosher salt, 1 tsp onion powder, ½ tsp sugar, ½ tsp cayenne, 1 tsp dried oregano
Add the flour and stir with a wooden. The dough will be very thick and sticky. It should form a ball. Continue to heat the dough in the saucepan until an internal temperature reaches 170°F, about 5 minutes. Remove from the heat and let the dough cool to 140°F.
1¼ cups bread flour
Transfer the dough to a bowl of your mixer with the paddle attachment.
One at a time, add the eggs, mixing on medium speed until each is incorporated into the dough.
4 large eggs
On low speed, mix in 1 cup of Parmesan, the bacon, and the chives until just combined.
1¼ cups Parmesan cheese, 1 tbsp chives
Transfer the dough to a pastry bag fitted with a ½-inch tip. Pipe about 2 inches of the dough onto each circle on the parchment paper. Press the tips of the dough down with moistened fingers. (have a small bowl of water nearby).
Top the puffs with equal amounts of the remaining Parmesan.
Bake until puffed and golden, about 20 minutes. Turn the oven off and use a large wooden spoon to crack the oven open for 15 minutes (see video for reference). Serve warm.