1. Grease a 9-inch springform pan and line the bottom with parchment paper. Preheat oven to 350°F (175°C).

2. Melt 1/2 cup unsalted butter. In a mixing bowl, whisk together melted butter and 1 cup granulated sugar until smooth. Add 2 eggs and 1 teaspoon vanilla extract; whisk until glossy.

3. Sift in 2/3 cup all-purpose flour, 1/2 cup unsweetened cocoa powder, and 1/4 teaspoon salt. Stir until just combined. Spread batter evenly into prepared pan.

4. Bake brownie layer for 18–20 minutes, until edges are set but center is soft. Let cool slightly.

5. In a large bowl, beat 24 ounces cream cheese until smooth. Gradually add 1 cup sugar and blend well. Mix in 1 cup sour cream. Add 3 eggs, one at a time, mixing just until combined. Stir in 2 teaspoons vanilla.

6. Pour cheesecake batter gently over cooled brownie layer and smooth top.

7. Lower oven temperature to 325°F (163°C). Bake cheesecake for 50–60 minutes, until center is set but slightly wobbly.

8. Turn off oven, crack door, and let cheesecake cool inside for 1 hour. Then cool to room temperature, and refrigerate at least 4 hours or overnight.

9. Heat 3/4 cup heavy cream until simmering. Pour over 1 cup semi-sweet chocolate chips, let sit 2 minutes, then stir until smooth. Spread ganache over chilled cheesecake.

10. Decorate with 1 cup whipped cream, 1/4 cup mini chocolate chips, and mint leaves if desired. Slice and serve.