Line a small baking sheet with parchment paper. Scoop 1 teaspoon sized balls of dulce de leche and set onto the baking sheet, with a bit of room between each. You will use a bit more than half of the can. Reserve the rest.
Freeze the dulce balls 15 minutes. Remove from the freezer and roll into more cohesive balls. No need for perfection! Set back in the freezer while you continue with the remaining recipe steps.
Preheat oven to 350 degrees. Line two large baking sheets with parchment.
In a large bowl, cream the butter and sugars until fluffy, about 2-3 minutes. Whip in the egg until fully incorporated, then the egg yolk. Beat in the vanilla.
In a separate bowl, whisk together the flour, cocoa powder, espresso powder (if using), cinnamon, cayenne pepper, baking soda, and salt. In two turns, beat into the butter mixture until just combined. Fold in the remaining dulce de leche (about 1/3 cup) and the chocolate chips.
Scoop a 1 - 1 1/2 tablespoon sized ball of cookie dough into your palm and flatten slightly. Set a frozen dulce de leche ball in the center and press the dough to cover the ball. Roll between your palms into a sphere. This dough is somewhat sticky, so you may have to wash your hands frequently. Or lick them. Then wash them. Set the dough balls on the baking sheet, no more than 6 at a time. In between batches of cookies, set the dulce de leche balls back in the freezer.
Bake cookies for 8 minutes. Tap the pan against the countertop to flatten the tops, then bake an additional 2-3 minutes until the edges are set but the center is still doughy. Let cool on the baking sheet - cookies will continue to cook gently. Serve warm, or seal in an airtight container for up to 3 days at room temperature, or 3 months in the freezer.