Preheat oven to 400 degrees Fahrenheit (204 degrees Celsius).
Using a paring knife, butterfly each chicken breast or cut a deep pocket into the thickest side, being careful not to cut through the opposite side.
Insert 1 ounce of mozzarella cheese into each pocket and secure the opening with 2-3 toothpicks.
In a shallow dish, combine flour with garlic powder, salt, and pepper.
Prepare a second dish with whisked eggs and a third dish with breadcrumbs mixed with 0.25 cup of grated parmesan.
Dredge each stuffed breast in the flour, dip into the egg wash, and press firmly into the breadcrumb mixture to ensure an even coating.
Heat olive oil in a large oven-safe skillet over medium-high heat.
Sear the chicken for 3-4 minutes per side until the breading is golden brown.
Spread marinara sauce over the top of each chicken breast and sprinkle with the remaining 0.25 cup of parmesan cheese.
Transfer the skillet to the oven and bake for 15-18 minutes, or until the internal temperature reaches 165 degrees Fahrenheit (74 degrees Celsius).
Remove toothpicks and garnish with fresh basil before serving.