I just made this tonight and everyone loved it including me!
All you need is:
2 larger, flatter boneless skinless chicken breasts
2-3 thin slices of onion, diced
2 tablespoons of minced garlic
1/2 cup of crumbled feta
2-3 tablespoons mayonnaise
10 oz fresh chopped spinach
Mix the onion, garlic, spinach, and feta together (making the feta more powdery by crushing it with a fork works well). If the chicken breasts aren't flat enough to fold, use a meat mallet it makes it more tender too. With the chicken breasts laying flat, spread a small amount of mayonnaise on the top. Next put the mixture in a line in the middle of the chicken breast. Then fold the chicken breast over like a taco or a burrito if it's thin enough, and wrap twine around the chicken to hold it. I also put olive oil on the top. Finally put the chicken in the oven with a partial foil covering on 400 degrees. Bake for half an hour, then remove the foil for another 10-15 min. I made rosemary red potatoes with olive oil for my side.
Hope you enjoy! ^_^