01 - Preheat oven to 350°F. Line a 24-cup mini muffin tin with paper liners or grease each cup lightly.
02 - Whisk melted butter and granulated sugar in a medium bowl until smooth. Add egg, vanilla extract, and red food coloring; mix until fully combined.
03 - Sift in flour, cocoa powder, and salt. Stir until just incorporated—avoid overmixing to maintain fudgy texture.
04 - Beat softened cream cheese, sugar, egg yolk, and vanilla extract in a small bowl until smooth and creamy.
05 - Spoon approximately 1 tablespoon of brownie batter into each muffin cup. Top with 1 teaspoon of cream cheese mixture.
06 - Use a toothpick or skewer to gently swirl the cream cheese into the brownie batter, creating a marbled pattern.
07 - Bake for 23 to 25 minutes until centers are set and a toothpick inserted comes out with moist crumbs.
08 - Let cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before serving.