In the bowl of a standing mixer, cream butter and sugar until creamy, about 2 minutes. Beat in egg and almond and vanilla extracts. Mix in flour and salt until combined.
Using a tablespoon cookie scoop, portion out balls of dough. Shape each ball into a log shape about 3 inches long. Place on a parchment-lined baking sheet. Place in the refrigerator to chill for 20-25 minutes.
Preheat oven to 375 degrees.
Bake for 9 minutes until set, but not brown. Let cool for 3-4 minutes before transferring to a cooling rack.
To decorate the cookies, chop the chocolate and add ⅔ to a double boiler or a heat-proof bowl set over a pan of gently simmering water. Stir until melted. Remove from heat and add the remaining ⅓ chocolate. Stir until completely melted. Dip each end of the cookies in the melted chocolate and gently shake off the excess chocolate. Place on parchment paper and sprinkle with nonpareils. Once the chocolate is set, store in an airtight container.