For the brownie batter:
4 large eggs
1¼ cups baking cocoa
1 teaspoon salt
1 teaspoon baking powder
1 Tablespoon instant espresso powder, mixed with 2 teaspoons water
2 teaspoons vanilla extract
2¼ cups sugar
1 cup unsalted butter, melted
1½ cups all-purpose flour
For the cheesecake filling:
1 (8-oz.) package cream cheese, softened
3 Tablespoons sugar
1 large egg yolk
Preheat the oven to 350ºF.
In a large bowl, whisk together the eggs, baking cocoa, salt, baking powder, espresso mixed with water, and vanilla until well combined.
Stir in the sugar and melted butter until well combined, then stir in the flour. (A firm rubber spatula works best.) Set brownie batter aside.
In a separate bowl, prepare the cheesecake filling by stirring together the cream cheese, sugar and egg yolk until well combined. Transfer the mixture to a pastry bag or plastic bag.
Grease a non-stick mini-muffin pan with cooking spray or butter and then spoon a tablespoon of brownie batter into the greased cups. Pipe a generous amount of cheesecake filling atop the brownie batter, and then top off each cup with an additional teaspoon of brownie batter.
Bake for about 12 minutes, or until a toothpick inserted comes out clean.
Let the brownie bites cool for 10 minutes in the pan and then transfer them to a cooling rack to continue cooling, or enjoy warm.