Prepare all ingredients and ensure butter is softened at room temperature.

Mix softened butter and brown sugar until creamy.

Add egg yolks and continue mixing until fully incorporated.

Add vanilla extract and mix well.

Sift flour, baking soda, and salt into the mixture and fold gently.

Add milk and mix until the dough is smooth.

Transfer the dough into a piping bag and cut a small opening at the tip.

Pipe small rounds of dough onto a baking sheet, approximately the size of a coin.

Optionally, place a chocolate piece in the center of each cookie for decoration.

Bake in a preheated oven at 160°C (320°F) for 12 minutes.