Preheat your oven to 425 degrees F. Lay each chicken breast on a flat surface. Place your non-cutting hand on top, and with a small knife, carve a flap/pocket into each chicken breast. Don't cut all the way through!

Heat a small pan and saute the onions and garlic in the olive oil for 1-2 minutes, until fragrant. Season with a pinch of salt and pepper. Set aside.

In a mixing bowl, combine the cream cheese, spinach, garlic, onions, mozzarella and Parmesan. Mix until the cream cheese is evenly distributed.

Place 1/4 of the filling into each pocket and flatten slightly to seal the filling in.

Starting from the top of the breast, wrap one bacon strip around the 1st half of the chicken breast. Repeat with a second slice. You can stretch the bacon a bit to wrap the whole breast evenly. Repeat with the other chicken breasts.

Place the chicken breasts onto a cooling rack, and place the rack onto a baking pan. Cook at 400 degrees F for 35-40 minutes, until cooked through (175F internal temperature). Turn once during the cooking process to cook the bacon evenly.