Preheat your oven to 325°F (165°C) and line a muffin tin with cupcake liners. In a mixing bowl, combine melted butter and granulated sugar until well blended. Next, whisk in room temperature eggs and vanilla extract.

In a separate bowl, mix together cocoa powder, all-purpose flour, and salt, then fold this dry mixture into your wet ingredients. Finally, stir in mini chocolate chips.

Spoon the brownie batter into each cupcake liner, filling them about one-third full. Bake for approximately 10-12 minutes, or until set around the edges but still slightly soft in the center.

In a mixing bowl, beat softened cream cheese until smooth and creamy. Gradually mix in granulated sugar until fully incorporated, then add eggs one at a time, mixing well after each addition. Lastly, add sour cream and vanilla extract until smooth.

Pour the cheesecake mixture over the brownie layer, filling each cup to the brim. Place the muffin tin in a larger pan filled with hot water and bake for an additional 20-25 minutes.

To prevent cracking, turn off the oven and leave the door ajar, allowing the cups to cool for 30 minutes. Cool completely at room temperature before refrigerating for at least 4 hours or overnight.