Take butter, vanilla extract, egg, and powdered sugar in a large mixing bowl and beat with an electric hand mixer until combined and turns fluffy.
Add flour, and salt into the butter mixture in batches and mix all together to form a dough.
Take a piping bag fitted with an open star tip nozzle and fill half of the cookie dough into the bag.
Pipe cookies into a swirl pattern on a greased baking tray.
Bake the cookies for 10-12 minutes. Once done place the cookies on a wire rack to cool completely.
Combine chocolate chips and butter in a microwave-safe bowl and heat it in the microwave at 20-second intervals; stirring properly after each interval and reheating as necessary.
Dip half of each cookie in the melted chocolate and transfer to a wire rack, decorate with sprinkles.
Allow chocolate to harden before enjoying.
Notes
You can store the cookies in an air-tight container for 3-4 days at room temperature or around 10-12 days in the refrigerator.