Adapted from 'Baking From My Home To Yours', by Dorie Greenspan
350 degrees. Line 2 baking sheets with parchment paper
2-1/2 cups all purpose flour
1 teaspoon baking soda
1/8 teaspoon salt
2 sticks of unsalted butter - room temperature
3/4 cup store-bought dulce de leche, plus 3/4 cup for filling (Or make your own like I did - recipe follows)
3/4 cup packed light brown sugar
1/2 cup sugar
2 large eggs
Whisk together the flour, baking soda and salt. Set aside
Working with a stand mixer fitted with a paddle attachment, beat the butter until soft. Add the 3/4 cup dulce de leche and both sugars and continue to beat until it's light and fluffy. (approximately 3 minutes) Add the eggs and beat for 1 minute. The mixture may look a little curdled, but it'll smooth out after the flour mixture goes in. Reduce the speed to low and add the dry ingredients. Mix only until they disappear into the batter.
I used a '1 level tablespoon cookie scoop', and baked the cookies for 14 minutes.
The cookies will be honey brown with a light crust, but they will still be soft. Remove the sheet from the oven, but leave them on the hot sheet for a couple of minutes. Then remove them onto a rack to continue cooling.
When the cookies are completely cool spread the flat bottoms of half the cookies with a small amount of dulce de leche, and sandwich the flat side sides of the remaining cookies
Homemade Dulce De Leche
I can never find Dulce De Leche, so I have to make my own. It's easy to do!
Empty 2 cans of sweetened condensed milk into a large microwave safe bowl. I used a very large Pyrex mixing bowl. It will overflow in anything smaller than a large bowl.
Microwave on medium power for two minutes.
Remove from the microwave and stir with a wire whisk. Be very careful; the mixture and bowl will get very hot! Once it gets hot putting in the cool whisk may make it boil up a bit, so use a pot holder
Microwave on medium power for another two minutes. Remove and whisk again
Microwave on medium-low power for 16-24 minutes or until it turns thick and caramel color, stirring every two minutes.