Prepare the Brownies: Begin by preheating your oven and greasing a baking pan. Follow the instructions on the brownie mix box to combine the ingredients, usually requiring you to mix the brownie mix with water, oil, and eggs according to the package instructions. Once mixed, pour the batter into the greased pan and bake as directed. Let the brownies cool completely in the pan.
Make the Cookie Dough: While the brownies are cooling, prepare the cookie dough. In a medium mixing bowl, cream together 1 cup unsalted butter and 1 cup brown sugar until light and fluffy. Add 1 tsp vanilla extract and 1/2 tsp salt, mixing until combined.
Add the Dry Ingredients: Gradually mix in 1 cup all-purpose flour until the dough is smooth and well-combined. Be careful not to overmix, as this can lead to tough cookie dough.
Incorporate Chocolate Chips: Fold 1 cup chocolate chips into the cookie dough, ensuring they're evenly distributed throughout.
Cut Brownies: Once the brownies have cooled, cut them into small squares. Size can vary; however, 2-inch squares are typically a good size for this recipe.
Assemble the Bombs: Take a spoonful of cookie dough and roll it into a ball. Place the cookie dough ball on top of each brownie square. Gently fold the edges of the brownie over the cookie dough, enclosing it in the brownie. Ensure that the edges are sealed well.
Drizzle with Sweetened Condensed Milk: If you desire, drizzle some 1 can sweetened condensed milk over the assembled brownie bombs for added sweetness and creamy flavor.
Chill: Place the brownie bombs in the refrigerator for about 30 minutes to firm up before serving.