In a large mixing bowl, combine softened butter and sugar until creamy.
Add egg yolks and vanilla extract, then mix until well combined.
Gradually add flour and baking powder to prepare a soft dough.
Knead gently until smooth, then refrigerate the dough for about 20–30 minutes.
Roll out the dough on a lightly floured surface to approximately ½ cm thickness.
Cut the dough into small round biscuit shapes using a cookie cutter.
Place the biscuits on a lined baking tray.
Bake in a preheated oven at 180°C (350°F) for 10–12 minutes until lightly golden.
Allow the biscuits to cool completely.
Spread a generous layer of dulce de leche on one biscuit and gently place another biscuit on top.
Press lightly to create a sandwich cookie.
Dust with powdered sugar and serve with tea or coffee.