114-oz cansweetened condensed milkwe like Eagle brand
For the thumbprint cookies
1cupunsalted buttersoftened
1/2cupconfectioners sugar
2egg yolks
2 tspvanilla extract
2 1/2cupsall-purpose flour
1/4tspsalt
1/2cupunsweetened flaked coconut
1/2cup dulce de leche
2tbsp flaky sea salt
Instructions
For the dulce de leche
Remove the paper label from the outside of the can and clean off the adhesive.
Fully submerge the can on its long side in a large pot of water. The can should be covered by at least two inches of water to ensure that the heat is distributed evenly. This prevents burning, or (rumored) explosions.
Bring the water to a boil, then simmer on low heat for 2 hours for a light caramel color, and 3 hours for a dark nutty brown color, checking the water level every 30 minutes to ensure that there is at least 2 inches of hot water above the top of the can. Add more water as needed. Yes, a little bit of patience is required.
Use tongs to remove the hot can to a wire rack and let cool to room temperature.
Place the butter in the bowl of a stand mixer using the paddle attachment. Cream at high speed for 2 minutes until very light and fluffy.
Add confectioner's sugar and cream for another minute.
Add the egg yolks, one at a time.
Add the vanilla. Stir in the flour and salt on low speed.
Pour the coconut in a shallow bowl. Use a cookie scoop to form balls with the cookie dough.
Roll the ball between your hands to smooth it out, then roll the ball in the coconut. Put each ball on the baking sheet and use a 1/2 teaspoon measuring spoon to create an indentation at the top of each ball.
Place cookie sheet in freezer for 15 minutes so that the butter can harden up and minimize the spread of the cookies. Meanwhile, preheat oven to 350 F.
Place the dulce de leche in a piping bag fitted with a 1/4 inch piping tip. Fill each indentation with caramel sauce.
Bake 8-10 minutes until the edges are golden brown. Remove to a wire rack and let cool. Sprinkle the tops with flaky sea salt.
Notes
The unopened can will keep for up to three months at room temperature. Once opened, the dulce de leche keeps for about three weeks in an airtight container.Since the can is sealed, it creates its own pressure cooker, so there's no need to use an instant pot. If you hate keeping an eye on a boiling pot, you could use a slow cooker for the same time periods, rather than this stovetop version.