01 - Preheat oven to 350°F. Line a 24-cup mini muffin tin with paper liners or lightly grease each cup.
02 - In a medium bowl, whisk together melted butter and sugar until smooth. Beat in egg, vanilla, and red food coloring until fully combined.
03 - Sift in flour, cocoa powder, and salt. Gently fold until just combined. Do not overmix.
04 - In a separate bowl, beat cream cheese until smooth. Add sugar, egg yolk, and vanilla; mix until creamy and lump-free.
05 - Spoon about 1 tablespoon of red velvet batter into each muffin cup. Top with 1 teaspoon of cheesecake mixture. Swirl gently with a toothpick or skewer for a marbled effect.
06 - Bake for 22 to 25 minutes, or until the centers are just set and the edges pull slightly away from the sides.
07 - Cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.