Preheat and Prep: Start by heating the oven to a steady roasting temperature. Lightly oil a large baking sheet so everything cooks evenly without sticking.
Season the Chicken: Place chicken thighs in a bowl. Add Dijon mustard, lemon juice, olive oil, onion powder, salt, and black pepper. Toss until each piece looks well coated and glossy.
Prepare the Brussels Sprouts: Add Brussels sprouts to a separate bowl. Toss them with olive oil, garlic, salt, and pepper until evenly covered.
Assemble the Pan: Arrange the chicken thighs on the baking sheet. Scatter Brussels sprouts around the chicken. Sprinkle chopped bacon over everything so the fat melts and flavors the pan.
Bake Until Golden: Slide the tray into the oven and bake until the chicken cooks through and the Brussels sprouts turn tender with crisp edges. Bacon should look browned and fragrant.
Finish and Garnish: Remove the pan from the oven and let it rest briefly. Sprinkle fresh parsley over the top and add a squeeze of lemon for extra freshness.
