Lay a sheet of acetate or parchment or a nonstick baking mat (smooth-side up) on a work surface. Place the mint leaves on the sheet, face down, about 2 inches apart.
Melt the chocolate over a water bath. Use a spoon or pastry bag to cover each mint leaf with a teaspoon of melted chocolate. Working carefully, place another sheet of acetate or baking mat (smooth side down) over the first one. Gently press down directly on top of each leaf to spread the chocolate around the leaf, making a border about 1/4-inch wide all around (don't worry if they're not very neat). Let set at least 1 hour, until firm. Gently peel off the acetate. Store in an airtight container for up to 3 days. Serve on a platter with the mint leaf showing.