How to Make It
Cream together butter and powdered sugar with mixer until lightened, about 3 minutes. Add egg and beat on medium-high until fully combined and fluffy, about 2 minutes. Add vanilla extract, peppermint extract, and drops of green food coloring to reach desired color. Add flour, baking powder, and salt. Mix on low until combined, about 1 minute. Wrap dough in plastic wrap and refrigerate for at least 30 minutes.
Preheat oven to 325°F. Line a baking sheet with parchment paper. Divide dough into 1 tablespoon portions. Roll dough into balls before rolling out into cylinders that are 4 1/2-inches long. Place cylinders on baking sheet. Gently pinch cylinders on either side of the middle of each cylinder and near the end of one side of the cylinder to create the illusion of the middle and front knuckles of a finger. Use a toothpick to press three parallel lines on the center knuckle and two parallel lines on the front knuckle. Press an almond slice at the end of the cookie just above the front knuckle to give the illusion of a fingernail. Freeze cookies for 30 minutes.
Bake cookies until puffed and baked through, 15 to 17 minutes. Gently remove almonds from cookies and squirt a small line of red decorating gel where the nail meets the nail bed. Return almonds to their places on each finger.
In a long shallow dish, melt chocolate in the microwave by heating in 30 second intervals at 30% power, stirring between each interval, until completely melted. Place each finger in the chocolate, just coating the underside of each cookie. Lift the cookie, gently scraping off excess chocolate, and place on a parchment paper-lined surface until chocolate has hardened, about 1 hour.