Turn your oven to 350°F (175°C) so it's hot and ready for baking.

Mix softened butter and sugar in a bowl. Add the egg and vanilla, and mix. In another bowl, whisk flour, baking powder, and salt. Combine the dry ingredients with the wet ones.

Now, Roll the dough into 1-inch balls and place them on a baking sheet lined with parchment paper. Flatten each ball slightly with a glass or your hand.

Bake in the oven for 10-12 minutes until the edges are golden. Let cool on the baking sheet for a few minutes, then move to a wire rack.

Beat softened butter in a bowl until creamy. Gradually mix in powdered sugar. Add milk and vanilla, and beat until smooth.

Spread frosting on cooled cookies and add some sprinkles if you like.

Allow the frosted cookies to sit for a few minutes to let the frosting set before eating or storing. Enjoy.