Preheat the oven to 325°F (163°C). Lightly grease or line a mini muffin pan or an 8-inch baking pan.
In a mixing bowl, whisk together the melted butter and sugar until combined.
Add the egg and vanilla extract. Mix until smooth.
Fold in the sifted cocoa powder and flour until a thick brownie batter forms.
Spread the brownie batter evenly into the prepared pan or muffin cavities.
Par-bake for 10 minutes.
While the brownie layer bakes, prepare the cheesecake filling. Beat the cream cheese and sugar until smooth and creamy.
Add the egg and heavy cream. Mix until fully incorporated and silky.
Pour or spoon the cheesecake mixture over the partially baked brownie base.
Return to the oven and bake for 18 minutes, or until the cheesecake edges are set and the center has a slight jiggle.
Allow the Brownie Bottom Cheesecake Bites to cool completely at room temperature.
Refrigerate for at least 4 hours, or overnight for the best texture.
To make the ganache, heat the cream until warm and pour it over the chopped dark chocolate. Let sit for 1 minute, then stir until smooth and glossy.
Drizzle the ganache over the chilled cheesecake bites.
Sprinkle with mini chocolate chips before serving.