* 1 cup unsalted butter (2 sticks), softened
* 2 large eggs
* 2 cups light brown sugar, packed
* 1 tablespoon vanilla extract
* 2 cups all-purpose flour
* 1 teaspoon baking powder
* 1/2 teaspoon salt, or to taste
* 30 Rolo candies, unwrapped and halved
* half of one 13.4-ounce can dulce de leche
Preheat oven to 350F. Line an 9×13-inch baking pan with aluminum foil for easier cleanup, spray with cooking spray; set aside.
To the bowl of a stand mixer fitted with the paddle attachment or large mixing bowl and hand mixer, add the butter and beat on high power to cream it, about 90 seconds.
Add the eggs, brown sugar, vanilla, and beat until smooth and well incorporated. Add the flour, baking powder, salt, and mix until just combined, don’t overmix. Add the Rolos and beat momentarily to incorporate.
Turn the batter out into prepared pan, smoothing the top lightly with a spatula. It is a very thick batter and can be resistant to spreading easily, but take your time and smooth it out the best you can.
Evenly dollop half of the jar of dulce de leche in ping pong ball-sized ‘blobs’ using a spoon over the surface of the pan. Using the back of a spoon, swirl the dulce de leche over the top. I just did a back-and-forth pattern that wasn’t fancy and took about 10 seconds.
Bake for about 30 minutes, or until a toothpick inserted in the center should come out clean, or with a few moist crumbs, but no batter. Bars firm up as they cool. Cool for about 2 hours before slicing and serving. Bars will keep airtight at room temp for up to 1 week.