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

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

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

Add the room-temperature eggs one at a time, whisking until incorporated.

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

Beat the cream cheese until smooth, then mix in sugar and vanilla extract, followed by the egg yolk.

Spoon brownie batter into muffin cups, add cream cheese filling, and top with more brownie batter.

Swirl the brownie batter and cream cheese filling together using a toothpick.

Bake for 12 minutes, until centers are soft but set.

Let cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.