Tantalizingly Thick Dulce de Leche Cookie

Directions

1. Cream the butter, dulce de leche, sugars, salt, and baking soda in a small bowl. In order to do this, smear the mixture up against the sides of the bowl with a spoon to mash the butter into the other ingredients. Continue to stir and smear the mixture for about two minutes, or until the mixture is homogenous with no chunks of butter visible and has the fluffy consistency of frosting. It might be a bit grainy from the sugar still but do not worry about this.
2. Add the egg yolk to the butter mixture and stir vigorously for about 30 seconds to create a homogenous mixture.
3. Add half of the flour and stir to incorporate.
4. Add the remaining flour and chocolate chunks and stir until the flour is incorporated and the chocolate chunks are evenly distributed.
5. Leave the dough in the bowl and cover with plastic wrap. Refrigerate for an hour.
6. Remove the dough from the refrigerator and form it into a ball. This ball should be slightly taller than it is wide and can be rough. Wrap the dough ball in plastic wrap and freeze for 6 hours.
7. When the dough is ready to bake, preheat the oven to 425 degrees F and line a baking sheet with parchment paper.
8. Once the oven has preheated to 425 degrees F, turn it down to 376 degrees F. Unwrap the dough ball and place it in the center of the baking sheet. Bake the cookie for 15-20 minutes, or just until the exterior has browned. For a properly doughy cookie, err on the side of underbaking.
9. Remove the cookie from the oven and place it, still on the pan, on a baking sheet. You can let it cool completely or eat it immediately after baking for maximum gooeyness!