Preheat and prep: Heat the oven to 425°F (220°C). Line a sheet pan with parchment or lightly oil it.
Pat the chicken thighs dry with paper towels to help the crust adhere and promote browning.
Mix the crust: In a bowl, combine Parmesan, panko, flour, garlic powder, onion powder, paprika, oregano, pepper, and 3/4 teaspoon salt. Stir in 2 tablespoons olive oil until the mixture looks like damp crumbs.
Make the binder: In a separate shallow bowl, whisk the egg with Dijon mustard. This step helps the crust stick and adds a slight tang.
Season the chicken: Lightly season the thighs with a pinch of salt on both sides.
This layers the seasoning so the chicken itself is flavorful under the crust.
Coat the chicken: Dip each thigh in the egg mixture, letting the excess drip off. Press the chicken into the Parmesan mixture, coating the top and sides well. For extra crunch, gently press more coating onto the top.
Arrange on the pan: Place thighs skin-side up on the prepared pan.
Leave space between them so hot air can circulate and crisp the crust.
Bake: Roast for 30–35 minutes, until the crust is golden and the thickest part of the chicken reaches 165°F (74°C). If needed, broil for 1–2 minutes at the end for a deeper golden top—but watch closely to avoid burning.
Rest and garnish: Let the chicken rest for 5 minutes. Finish with a squeeze of lemon and a sprinkle of parsley.
Serve hot.