01 - Preheat oven to 350°F. Line a 24-cup mini muffin tin with paper liners or lightly grease each cup with cooking spray.
02 - In a medium bowl, whisk together melted butter and granulated sugar until smooth and glossy. Beat in egg, vanilla extract, and red food coloring until fully combined and uniform in color.
03 - Sift flour, cocoa powder, and salt into the wet mixture. Gently fold with a spatula until just combined—do not overmix to maintain fudgy texture.
04 - In a separate bowl, beat cream cheese with an electric mixer until completely smooth. Add sugar, egg yolk, and vanilla; mix until creamy and no lumps remain.
05 - Spoon approximately 1 tablespoon of red velvet batter into each muffin cup. Top with 1 teaspoon of cheesecake mixture. Use a toothpick to swirl gently for a marbled effect.
06 - Bake for 22 to 25 minutes until centers are just set and edges pull slightly away from the sides. The tops should feel firm but slightly springy to the touch.
07 - Let cool in the pan for 10 minutes before transferring to a wire rack. Allow to cool completely before serving for best texture.