Preheat your oven to 350°F (175°C).

In a medium saucepan, melt the unsalted butter and semisweet chocolate chips over low heat, stirring constantly until smooth.

Remove from heat and let it cool slightly.

In a mixing bowl, whisk in granulated and brown sugars until fully combined.

Add eggs one at a time, beating well after each addition, followed by the vanilla extract.

In a separate bowl, whisk together flour, salt, and baking powder, then gradually fold this into the chocolate mixture.

Pour the brownie batter into the prepared springform pan and smooth it out. Bake for 20 to 25 minutes, until set but slightly soft in the center.

Remove from the oven and let it cool.

In a large mixing bowl, beat the cream cheese and sugar together until smooth.

Add eggs one at a time, beating on low speed to keep it light and fluffy.

Mix in the vanilla extract and sour cream until the batter is smooth.

Carefully pour the cheesecake batter over the cooled brownie layer and spread it evenly.

Bake for 40 to 45 minutes, until the edges are set and the center slightly wobbles. Let it cool on a wire rack.

In a small saucepan, heat the heavy cream until it begins to simmer.

Remove from heat and add chocolate chips, letting it sit for 2 minutes before stirring until smooth.

Remove the cheesecake from the springform pan and place it on a serving platter.

Pour the ganache over the top, allowing it to drip over the edges.

Garnish with sprinkles, whipped cream, and berries to personalize.