Get a large bowl and inside it cream together the softened butter, sugar and egg with an electric mixer.
Add the vanilla extract, then gradually add the flour, baking powder and salt (through a sift). Whisk again on low speed until it's fully combined.
Mould the cookie dough into a sphere shape and tranfer the cookie dough to plastic wrap. Chill the cookie dough for 30 minutes in the fridge.
Flour a flat surface and roll the dough out to about 1/4 of an inch thick. Cut out shapes with a circular cookie cutter and transfer carefully to the baking sheet.
Bake for 15 minutes until the cookies are slightly golden brown around the edges.
Once the cookies have cooled, dip each one into the melted chocolate and straight away sprinkle on the sprinkles. Repeat the process for all sugar cookies and leave to set. It is now ready to be served.