Pat chicken pieces dry with paper towels—this ensures proper browning and caramelization rather than steaming. Heat olive oil in a large skillet over medium-high heat until shimmering, approximately 1 minute.

Season chicken with salt and pepper, then sear until golden brown on all sides, 8–10 minutes total. Transfer to a plate; don't worry if it's not fully cooked through yet.

In the same skillet, melt butter and sauté diced onion until softened, about 3 minutes. Add minced garlic and cook until fragrant, roughly 30 seconds, stirring constantly to prevent burning.

Stir in tomato paste, Italian seasoning, and paprika, cooking for one minute to bloom the spices. Pour in chicken broth and heavy cream, whisking to combine smoothly without lumps forming in the sauce.

Return the saucy crowd chicken skillet pieces to the pan and add sliced mushrooms and bell pepper. Simmer for 10–12 minutes until chicken reaches 165°F internally and vegetables become tender.

Stir in fresh spinach until wilted, approximately 2 minutes, then remove from heat and sprinkle Parmesan cheese on top. Taste and adjust seasoning with additional salt or pepper as needed before serving.