1 pound (about 2 to 3 medium) zucchini, grated
Kosher salt and black pepper
4 tablespoons unsalted butter at room temperature, divided
1 medium onion, finely chopped
1 large egg
1 cup sourdough bread crumbs (or panko)
1/3 cup whole milk ricotta cheese
1/4 cup grated Parmesan cheese
4 to 6 bone-in, skin-on chicken breasts, legs, or mix of both
Preheat the oven to 425°F.
Toss the grated zucchini with 1 tablespoon kosher salt and set in a strainer to drain for 15 to 30 minutes. Squeeze out any remaining water with a dish cloth or paper towels.
Melt 1 tablespoon butter in a large skillet over medium heat. Add the onion and cook until soft and translucent, 5 to 7 minutes. Add the drained zucchini and sauté until tender, another 3 to 5 minutes. Remove from the heat and allow to cool.
Add the egg, bread crumbs, ricotta, Parmesan, and remaining 3 tablespoons butter to the skillet and season with salt and pepper to taste. Mix until completely combined.
Gently loosen the skin from the chicken breasts, being careful not to tear. Stuff a few heaping tablespoons of the zucchini mixture (the more the better) under the skin of each breast.
Place the stuffed chicken in a large roasting pan and cook until the internal temperature reaches 160°F in the thickest part of the meat, about 50 to 60 minutes. Remove from oven and rest for 10 minutes (chicken will continue cooking with residual heat).