Step 1

Preheat the oven to 350 and line a baking sheet with a silicone liner. (In my experience, silicone liners prevent cookies from spreading too much in the oven).

Step 2

Next, make the cookies: In a medium-size bowl, add the butter and beat on medium speed with an electric mixer. Beat for about 10 seconds to break it up.

Step 3

Add the sugar to the butter, and beat until fluffy, about 45 seconds.

Step 4

Next, add the egg yolk, heavy cream, and vanilla. Beat to combine.

Step 5

Evenly sprinkle the flour, baking powder and salt over the batter, and beat until just combined.

Step 6

The dough will be a little softer than regular cookies, but you should still be able to work with it. (See note about using milk below).

Step 7

Press the dough down into the bottom of the bowl and use your hand to lightly score it in half. From each half of dough, you should get three balls of dough.

Step 8

Place each dough ball in your hands, and roll it into a perfect ball. Place each ball, evenly spaced, on the prepared baking sheet.

Step 9

Press the cookies to flatten them slightly.

Step 10

Bake for 14-15 minutes. The tops will appear dry when they're done.

Step 11

Let the cookies cool on the baking sheet for 1 minute before moving them to a wire rack to cool completely.

Step 12

Meanwhile, mix together all of the frosting ingredients (except the sprinkles) in a bowl using an electric mixer until light and fluffy.

Step 13

Frost the cookies once they have cooled, and decorate with sprinkles to serve.