Preheat & Prep: Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
Prepare Espresso Filling: In a small bowl, dissolve espresso powder in hot water, then mix in the condensed milk. Set aside.
Mix Dry Ingredients: In a bowl, whisk together the flour, baking soda, and salt.
Cream Butter & Sugar: Beat the softened butter and brown sugar until fluffy. Add the egg and vanilla, mix well.
Combine Dry & Wet Ingredients: Gradually mix in the dry ingredients until fully incorporated. Fold in chocolate chips.
Form Cookie Dough: Scoop a spoonful of dough, create a small indentation in the center, and fill with a little espresso filling. Seal the dough around it.
Bake: Drop dough balls onto the prepared baking sheet and bake for 10-12 minutes until golden around the edges.
Make Topping: While cookies cool, heat heavy cream in a small saucepan and pour over chocolate chips. Stir until smooth.
Swirl Topping: Drizzle the melted chocolate over the cooled cookies and swirl with a toothpick.