In a large bowl, beat the butter and powdered sugar until creamy. Add the vanilla extract and mix again. Finally, add the flour and mix until a firm dough forms. Wrap the dough in plastic wrap and let it rest in the fridge for about 1 hour.
Roll the dough into small balls. Place them on a baking sheet lined with parchment paper and press an indentation into each one. I used a measuring spoon from my set, but you can also use your thumb or the back of a wooden spoon.
Bake the cookies at 350°F (180°C) for 14 minutes. Let the cookies cool completely before filling and decorating.
Stir the dulce de leche so it softens slightly. You can spoon it into the cookies, or pipe it in using a piping bag (that’s what I did).
Melt the chocolate in a double boiler. Once melted, drizzle it over the cookies with a spoon, or use a piping bag if you prefer. Let the chocolate firm up before serving.
How to store
With caramel on top, the cookies will keep for about 2–3 days. Without the caramel, they’ll last much longer. Do note that once filled, the caramel makes the cookies a bit softer when stored in a tin.