Combine cinnamon, nutmeg, and sugar in a small bowl. Set aside.
Core apples, making sure not to puncture the bottom of the apples so that the juices will remain. Remove skin from 1/2-inch around top of apples at the opening. Fill each cavity with the cinnamon-sugar mixture. Top each apple with a teaspoon of butter. Place apples in casserole dish and pour apple juice around them. Cover pan with aluminum foil and bake for approximately 45 minutes to 1 hour. Remove from heat, garnish with fresh mint, and serve.