Fill a large pot with water, 3/4 full and set on medium high and bring to a boil. Set a tray next to the stove and cover with 3 layers of paper towels. Slice 2 inches off each cabbage bottom and remove any brown leaves. Core 3 inches into cabbage. Place one cabbage in boiling water and remove leaves as they heat and slip off, about 5 minutes. Keep all leaves, large and small. Set the leaves on tray to drain. Cook second cabbage same as above. Prepare Filling: Fry onions with 1 tablespoon oil until translucent. Remove from pan. Using the same pan, cook beef, add 1 tablespoon mint, garlic,1/2 cup lemon juice, salt and pepper and onions. Drain fat from pan and add rice, add remaining lemon juice and more mint if desired. Cover, reduce heat to a simmer, checking often for about 10 minutes, until mixture has thickened. Oil a baking dish, and place a layer of small broken leaves, 2-3 leaves thick. Add 1 layer of the meat/rice mixture, about 1 1/4 inches thick. Sprinkle 1 tablespoon mint and a little Feta cheese on top. Repeat layers ending with cabbage leaves (3 leaves thick) on top. Sprinkle leaves with olive oil, salt, pepper and the remainder of the Feta cheese. Bake uncovered at 375 for 30 to 35 minutes. If top begins to dry, add more olive oil. Serve with salad, bread and dipping oil. You may cut remainder into single servings and freeze.