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

Sift the cocoa powder in a medium mixing bowl to eliminate lumps.

Melt the unsalted butter and combine with sugar, cocoa powder, vanilla extract, red food coloring, salt, espresso powder, and vinegar.

Add the eggs one at a time, mixing thoroughly after each addition.

Gently fold in the all-purpose flour until just combined.

Beat the cream cheese with additional sugar until smooth; fold in the egg yolk.

Fill each mini muffin cup halfway with brownie batter, add cream cheese filling, then top with more brownie batter.

Gently swirl through layers with a toothpick.

Bake for approximately 12 minutes until tops are set.

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