Line a small square pan (8 x 8 or similar) with parchment paper or use sprayed aluminum foil.

In a microwave-safe bowl, mix chocolate chips, sweetened condensed milk, and butter. Heat in 20-second bursts in the microwave, stirring until melted (less than 2 minutes). Don't overcook.

Stir the melted chocolate mixture until smooth, then add 1 cup of chopped pecans and mix.

Pour half of the mixture into the prepared pan and smooth it with a spatula. Put it in the freezer briefly to set.

Warm the Dulce de Leche in the microwave as before, spoon it over the fudge, and smooth it out. Return to the freezer for a few minutes to set.

Take the pan out of the freezer, warm the remaining fudge mixture in the microwave, and spread it over the Dulce de Leche layer.

Sprinkle with chopped pecans.

Cover the pan with plastic wrap and refrigerate for at least 2 hours.

Remove the pan from the fridge, lift the parchment paper with the fudge out of the pan, and cut into small squares when ready to serve. Enjoy at room temperature.