Heat oil in a large skillet, over medium heat. Add spinach and cook 3-4 minutes, or until the spinach is wilted, mixing as it cooks.

Add garlic and cook an additional 30 seconds. Transfer spinach/garlic to a bowl.

Wrap chicken pieces, one at a time, in clear plastic wrap (to prevent making a mess) and pound down the chicken with a meat tenderizer until the chicken is very thin, about 1/2 of an inch.

Place 1 wedge of cheese on each piece of chicken and spread over 1/2 of each piece.

Divide the spinach between the pieces of chicken, carefully spreading out over the cheese.

(I found using my hands was easier for this step, but you could scoop out about 2 tablespoons spinach on each.)

Fold the 1/2 of the chicken with nothing on it over the 1/2 with the cheese and spinach.

Dip both sides of the chicken in the beaten egg and then in the breadcrumbs.

Spray the skillet you used for the spinach with cooking spray and transfer the chicken to the skillet. Cook chicken over medium heat 3-4 minutes on both sides, or until the chicken is slightly browned. I found it easiest to flip the chicken using tongs to hold it together. Spray chicken with cooking spray if the breading looks dry.

Turn heat down to medium-low heat. Cover skillet and cook an additional 4-6 minutes, or until the middle of chicken is fully cooked (this step will take more or less time, depending on the thickness of the chicken).

Sprinkle with salt and pepper, to taste.