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 - Whisk melted butter and granulated sugar in a medium bowl until smooth. Beat in the whole egg, vanilla extract, and red food coloring until fully combined and uniformly colored.
03 - Sift flour, cocoa powder, and salt directly into the wet mixture. Gently fold with a spatula until just combined—do not overmix to maintain fudgy texture.
04 - Beat softened cream cheese in a separate bowl until completely smooth. Add granulated sugar, egg yolk, and vanilla extract; mix until creamy and free of lumps.
05 - Spoon approximately 1 tablespoon of red velvet batter into each muffin cup, filling about halfway. Top each 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 of the cups. The tops should feel firm but slightly springy to the touch.
07 - Let cool in the pan for 10 minutes to set. Carefully transfer to a wire rack and cool completely before serving to allow flavors to develop fully.