Preheat the oven to 350°F. Lightly spray a mini muffin pan with cooking spray and set aside.
In a large bowl, mix together the eggs, cocoa powder, baking powder, cold brew concentrate and vanilla until fully combined. Mix in the sugar and butter. Fold in the flour until just combined. Set aside.
In the bowl of a stand mixer, cream together the cream cheese, sugar and egg yolk until smooth.
Scoop around 1 Tbsp of brownie batter into each muffin cavity. Spoon some cream cheese mixture on top of the brownie batter.
Bake in the preheated oven for 12 minutes, or until a toothpick inserted comes out clean.
Allow brownies to cool in the pan for around 10 minutes, then transfer to wire racks to cool completely.