Instructions

• Preheat the oven to 350°F. Line a 9x13-inch baking pan with aluminum foil, spray the foil with cooking spray, and set the pan aside.
• In the bowl of a stand mixer fitted with the paddle attachment (or in a large mixing bowl using a hand mixer), add the softened butter. Beat on medium-high until light and creamy, about 90 seconds, scraping down the bowl once.
• Add the eggs, packed light brown sugar, and vanilla extract to the butter. Beat until the mixture is smooth and well combined, stopping to scrape the sides and bottom of the bowl as needed.
• Add the all-purpose flour, baking powder, and salt. Mix on low speed (or stir with a spatula) just until the dry ingredients are incorporated and no large streaks of flour remain. Do not overmix.
• Ensure the 30 Rolo candies are unwrapped and halved (as listed). Gently fold the halved Rolos into the batter with a spatula until they are evenly distributed.
• Turn the thick batter into the prepared pan and smooth the top as best you can with an offset spatula or the back of a spoon. The batter will be dense and may resist spreading.
• Spoon half of the can of dulce de leche into ping-pong-ball-sized dollops evenly across the surface of the batter.
• Use the back of a spoon to lightly swirl the dulce de leche into the batter in a back-and-forth or figure-eight pattern to create a marbled top. Do not over-swirl.
• Bake in the preheated oven for about 30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs but no raw batter.
• Remove the pan from the oven and cool on a wire rack until the bars are set, about 2 hours. Use the foil to lift the slab from the pan, then slice into bars and serve.