1. Arrange cookies, in a single layer, on a baking sheet. Transfer half of marshmallow to a large decorating bag fitted with a 1/2-inch plain tip or coupler. Pipe 1 mound, about 1 inch high, on each cookie. Let stand until set, at least 30 minutes or up to 1 hour.
2. Spread out nonpareils in a rimmed baking sheet; set aside. Melt chocolate and let cool slightly; transfer to a small bowl. Working with 1 cookie at a time, hold cookie and dip marshmallow top in chocolate, then turn to coat completely. Place, cookie side down, on nonpareils to coat bottom. Lightly sprinkle top with nonpareils. When tray is full, chill until set, 15 minutes. (Can be made ahead. Store in an airtight container in refrigerator up to 3 days.) Makes 50 cookies.
1. In a large mixer bowl, sprinkle gelatin over cold water and let stand until softened, about 5 minutes. Meanwhile, in a small saucepan, combine sugar and 1/4 cup water. Stir over medium-high heat until sugar dissolves. Using a pastry brush dipped in water, brush down sugar crystals on sides of pan. Place a candy thermometer into mixture. Boil (do not stir) until syrup registers 238 degrees F (soft-ball stage), about 10 minutes. Pour into gelatin. Using the whisk attachment, beat gelatin mixture on medium-low speed until slightly cooked, about 5 minutes. Increase speed to medium-high and beat to soft peaks, about 12 minutes. Stir in peppermint candies until combined. Tint with food coloring (if desired). Use immediately. Makes 4 cups.