Preheat a convection oven to 400°F (200°C).
In a medium mixing bowl, combine the softened cream cheese, chopped spinach, mozzarella, and 2 tablespoons of the Parmesan cheese until homogenous.
Using a sharp chef's knife, slice a horizontal pocket into the thickest part of each chicken breast, ensuring the blade does not penetrate the opposite side.
Divide the spinach and cheese mixture equally and stuff into each chicken pocket; secure the opening with two wooden toothpicks.
Prepare a standard breading station: bowl one with flour seasoned with half the salt and pepper; bowl two with beaten eggs; bowl three with panko breadcrumbs mixed with remaining Parmesan, garlic powder, and onion powder.
Dredge each stuffed breast in flour (shaking off excess), dip thoroughly in egg wash, and press firmly into the panko mixture to ensure full coverage.
Heat olive oil in a large heavy-bottomed oven-safe skillet over medium-high heat until shimmering.
Sear the chicken for 3 to 4 minutes per side until the breading is golden brown and crisp.
Transfer the entire skillet to the preheated oven and roast for 12 to 15 minutes, or until the internal temperature reaches 165°F (74°C).
Allow the chicken to rest for 5 minutes before removing toothpicks and serving.