Preheat your oven to 350°F (175°C) and grease a mini muffin pan.

Sift cocoa powder into a mixing bowl.

Melt the unsalted butter in a saucepan, then whisk in sugar, cocoa powder, vanilla extract, red food coloring, salt, espresso powder, and vinegar.

Add the eggs one at a time, mixing well for a smooth texture.

Fold in the all-purpose flour carefully.

In another bowl, blend cream cheese, sugar, and vanilla extract until smooth, then fold in the egg yolk.

Spoon brownie batter into the cups, add cream cheese mixture, and cover with more brownie batter.

Swirl the brownie and cream cheese mixtures gently with a toothpick.

Bake for about 12 minutes until slightly soft.

Cool in the pan for 5 minutes before transferring to a wire rack.