Chocolate Thumbprint Cookies

1. Cream the butter and sugar together on high with an electric mixer.
2. Add the egg and vanilla extract and mix until combined.
3. Slowly mix in the flour, cocoa powder and salt until the dough comes together.
4. Cover the dough and place in the refrigerator for 1 hour.
5. Preheat the oven to 350°F (180°C) and line a baking sheet with parchment paper.
6. Form the dough into balls and make an indent in the center either with your thumb or the back of a teaspoon.
7. OPTIONAL: If your cookie dough is warm, consider placing the formed cookies in the fridge for half an hour before baking to ensure they keep their shape in the oven.
8. Place the formed cookies on the baking sheet leaving a bit of space between them and bake for 12-14 minutes.
9. If the indent has puffed up during baking, gently press back down.
10. Let the cookies sit for 10 minutes and then remove to a wire rack to cool. 
11. Once the cookies are cool, fill with dulce de leche.

Homemade Dulce De Leche

1. Add the milk, sugar, salt and baking soda to a large heavy-bottomed pot.
2. Place the mixture on the stove over medium heat and let simmer for approximately 1-1.5 hours. Adjust the temperature so it remains at a good simmer; we don’t want the mixture to rapidly boil.
3. For the first 15 minutes keep a close eye on the mixture – the baking soda will cause the milk to expand and bubble considerably so you’ll need to stir the mixture regularly.
   After the bubbling subsides, check on and stir the dulce de leche every 5-10 minutes until it begins to turn a light brown color. That’s your signal to start stirring the dulce de leche more frequently to prevent burning.
4. When the mixture has slightly thickened and reached a deep brown color*, remove from heat and stir in the vanilla extract. Allow to cool to room temperature. Then store in an airtight container in the refrigerator until ready to use.