Preheat your oven to 350° F and then lay chicken breasts out on cutting board and cover top with plastic wrap. Using flat side of meat tenderizer, gently pound chicken breasts from center toward edges until ¼ inch thick.
Use your fingers to evenly distribute crushed garlic on meat surface and then evenly distribute feta cheese on both breasts, reserving some for garnish if desired. Next, layer spinach leaves on both chicken breasts.
Starting with short end of each chicken breasts, roll from end to end and then seal and secure with toothpicks. Trim ends of tooth pics to make flush with meat.
Heat olive oil on stove top, over medium high heat, using oven-safe saute pan. Place the chicken rollups in pan and brown and rotate to sear all surfaces. Cover saute pan (use foil if necessary) and it in oven for 20-25 minutes, until meat is cooked throughout