Preheat oven to 330° F / 165° C. Lightly grease an 8×8-inch / 20×20-centimeter square baking tin and line with parchment. Set aside until ready to use.

Melt butter in a saucepan over medium heat. When butter has melted, whisk in sugar, cocoa powder, espresso powder, and salt. Remove from heat and let mixture cool slightly, about five minutes, then transfer to a large mixing bowl.

Whisk eggs and vanilla bean paste into mixture, then sieve in the flour and whisk again to combine. Batter will be very thick.

Gently fold chopped chocolate and hazelnuts into the batter.

Reserve 3-4 tablespoons of brownie batter and set aside. Spread the rest of the batter into prepared baking tin. Using damp fingers or a spatula, press the batter evenly into the tin.

To make the cheesecake swirl, add cream cheese to a mixing bowl or the bowl of a stand mixer and whip on medium speed until fluffy. Add icing sugar, Nutella, egg, and salt and mix until until well-combined. Spread cheesecake mixture over brownie batter.

To the reserved brownie batter, add 1-2 tablespoons of milk. Drop the reserved brownie batter over cheesecake mixture by the spoonful, then use a knife or skewer to create a swirl pattern.

Bake in preheated oven for 40-45** minutes, or until a cake tester comes out clean.

Remove from oven. Transfer to a wire rack and allow to cool completely, at least one hour.

When brownies have cooled, remove from tin, slice into squares, and enjoy!

Store brownies in an airtight container at room temperature for up to three days.