In a medium saucepan, bring the milk almost to boiling (don't boil). Remove the milk from the heat. Stir in the 1 cup chocolate mint leaves. Cover and let mixture steep for 20 minutes.
In a bowl, beat eggs and sugar until combined, but not foamy. Strain milk and stir into egg mixture.
Place a 1-1/2-quart casserole or eight 6-ounce custard cups in a 13x9x2-inch baking pan or roasting pan on an oven rack. Ladle the custard into the casserole or the cups. Pour some boiling water into the baking pan around the casserole or the cups to a depth of about 1 inch.
Bake in 350 degree F oven for 45 to 50 minutes for casserole or about 25 minutes for custard cups or until a knife inserted near the center comes out clean. Serve warm or chilled, garnished with chocolate mint leaves and a chocolate curl, if you like. Makes 8 servings.