Preheat the oven to 375°F (190°C).

In a medium bowl, combine the softened cream cheese, shredded mozzarella, chopped spinach, garlic powder, onion powder, and a pinch of salt and pepper. Mix until even and spreadable.

Pat each chicken breast dry with paper towels. Using a sharp knife, cut a horizontal pocket through the thickest part of each breast, leaving the edges intact.

Spoon the filling into each pocket. Press the opening closed and secure with toothpicks if needed. Don’t overfill or the filling may leak.

Heat a skillet over medium heat and add olive oil. When the oil shimmers, sear the stuffed chicken 3–4 minutes per side until a golden crust forms.

Transfer the seared breasts to a baking dish. Bake in the preheated oven for 25–30 minutes, or until an instant-read thermometer inserted into the thickest part (not the filling) reads 165°F (74°C).

Remove from the oven and let the chicken rest for 5 minutes before slicing and serving.