Directions
In a separate bowl, whisk flour, baking soda and salt.
In a stand mixer with the paddle attachment, add the butter and beat on medium until it is creamy. Add the granulated sugar and brown sugar to the bowl and mix on medium until it is fluffy, about 3 minutes.
Mix the espresso powder and water together in a small bowl. Add this liquid, vanilla, and egg on low to combine to a smooth consistently. Slowly add in the flour/dry ingredients until just combined. Add in the chocolate on low until just evenly distributed.
Cover the bowl and chill the dough for at least 1 hour or preferably overnight.
Preheat the oven to 350˚F. Line 3 baking sheets with parchment or foil. Using a 3 tablespoon cookie scoop or a 1/4c measuring cup, form the dough into ~70g balls. For each of the dough balls: break it in half, make a dent in both of the halves and spoon in about a small spoonful of dulce de leche into one (about 5-6g). Place the other half of the dough on top and smooth the seam so the dulce is complete encapsulated.
Place about 5 balls spaced evenly apart on the pan and place in the freezer for 15 minutes.
Once chilled, place the sheet in the oven and bake for ~16 minutes. The cookies may spread out a bit, but that’s okay.
If you want perfectly round cookies, grab one of those round Chinese takeout containers (the clear plastic ones that soup come in). As soon as you take the cookies out of the oven, place the container upside down on top of each cookie, pushing in the edges so the cookie completely fits under the container and then swirl the container around a few times. This should round out the edges and give you cookies that are all round and the same size!