Ingredients
Equipment
Method
- Step 1: Prep Your Pan and Oven Preheat your oven to 350°F (175°C). Line a 9x13-inch baking pan with parchment paper, leaving an overhang on the sides for easy lifting. Lightly spritz the parchment paper with cooking spray or rub with butter.
- Step 2: Mix the Wet Ingredients In a large mixing bowl, whisk together the granulated sugar, eggs, and extra egg yolk until nicely combined and slightly paler. Pour in the melted butter, pure vanilla extract, and oil. Continue whisking until smooth and completely incorporated.
- Step 3: Combine the Dry Ingredients In a separate bowl, sift together the all-purpose flour, unsweetened cocoa powder (Dutch process recommended), cornstarch, and salt. Sifting helps prevent lumps and ensures a smooth brownie texture.
- Step 4: Create the Brownie Batter Gradually add the dry ingredients into the wet ingredients. Use a wooden spoon or rubber spatula to mix gently until just combined; be careful not to overmix. Fold in the semi-sweet chocolate chips.
- Step 5: Layer and Swirl Pour about half of the brownie batter into the prepared pan and spread evenly. Dollop spoonfuls of marshmallow creme over the batter. Carefully pour the remaining brownie batter on top. Use a knife to gently drag it through the layers to create swirl patterns.
- Step 6: Bake to Perfection Bake in the preheated oven for 28-32 minutes. The edges should be set, and a toothpick inserted into the brownie portion (avoiding marshmallow) should come out with a few moist crumbs. The marshmallow areas will puff up and achieve a light golden hue.
- Step 7: Cool and Serve Allow the brownies to cool completely in the pan before cutting. This allows them to set properly for clean slices. Once cooled, use the parchment paper overhang to lift them out, slice, and enjoy.
Notes
Tips for Success: Don't overmix the batter; mix until just combined to prevent tough, cakey brownies. It is crucial to cool brownies completely in the pan before cutting for clean, beautiful slices. Using a good quality cocoa powder, especially Dutch process, significantly enhances flavor and color. The parchment paper sling is essential for easy removal and neat cutting. For perfectly neat slices, use a sharp knife and wipe it clean with a damp cloth after each cut. You can mix dry ingredients ahead of time and store in an airtight container for quicker assembly.
Substitutions & Additions: Feel free to swap semi-sweet chocolate chips for dark chocolate chips, milk chocolate chunks, or a mix of white and dark. For extra texture, fold in ½ cup of chopped walnuts or pecans. A tiny splash (¼ teaspoon) of almond extract or peppermint extract can add a delightful warmth or festive twist. For even more marshmallow, sprinkle a cup of mini marshmallows over the brownies during the last 5-7 minutes of baking for a toasted, gooey effect. A sprinkle of flaky sea salt over the top right after baking enhances the chocolate flavor beautifully.
Storage: Once completely cool, store marshmallow brownies in an airtight container at room temperature for up to 3-4 days. For longer storage or in warm climates, store in an airtight container in the refrigerator for up to a week; a quick microwave zap (10-15 seconds) can bring back gooeyness. For long-term storage, wrap individual brownies tightly in plastic wrap, then place in a freezer-safe bag or container and freeze for up to 3 months. Thaw at room temperature or warm gently in the microwave.