1. Preparing the Cake Layer

1. Preheat the Oven:
   Set your oven to 350°F (175°C).
2. Prepare the Pan:
   Grease the bottom and sides of a 9 or 10-inch springform pan thoroughly to prevent sticking.
3. Sift Dry Ingredients:
   In a medium bowl, sift together:
   • 1 cup all-purpose flour
   • 1 ½ teaspoons baking powder
   • ¼ teaspoon salt
     Set aside.
4. Cream Butter and Sugar:
   In the bowl of a stand mixer fitted with the paddle attachment:
   • Beat ½ cup unsalted butter and ½ cup sugar on medium speed for about 2 minutes, until light and fluffy.
5. Add Egg and Vanilla:
   • Add 1 large egg and 1 teaspoon vanilla extract.
   • Mix until smooth, scraping down the sides as needed.
6. Incorporate Dry Ingredients and Milk:
   • On low speed, alternate adding the flour mixture and ½ cup milk, beginning and ending with the flour.
   • Mix until just combined to avoid a tough texture.
7. Bake the Cake Layer:
   • Pour the batter into the prepared pan and spread evenly.
   • Bake for 25 minutes, or until a toothpick inserted in the center comes out clean.
   • Remove from the oven, but do not remove from the pan.

2. Making the Cheesecake Layer

1. Lower the Oven Temperature:
   Reduce heat to 325°F (163°C).
2. Beat Cream Cheese Mixture:
   In a clean mixing bowl with paddle attachment:
   • Beat 24 oz (3 packages) cream cheese, 1 cup sugar, and 1 teaspoon vanilla extract on medium speed for 3–4 minutes, until completely smooth and lump-free.
3. Add Eggs:
   • In a small bowl, whisk 3 eggs with a fork.
   • Add them to the cream cheese mixture on low speed, mixing until just combined.
4. Stir in Sour Cream:
   • Add ¾ cup sour cream and gently stir until smooth and uniform.
5. Pour Over Cake Layer:
   • Pour the cheesecake batter over the cooled cake layer still in the springform pan.
   • Spread evenly.
6. Bake the Cheesecake:
   • Bake for 45–50 minutes, or until edges are set and the center jiggles slightly.
   • Do not overbake to avoid cracks.
7. Cool Gradually:
   • Cool on a wire rack for 15 minutes.
   • Run a knife around the edge to loosen.
   • Let cool to room temperature, then cover and refrigerate for at least 4 hours or overnight.

3. Creating the Chocolate Layer (Ganache)

1. Heat the Cream:
   • In a small saucepan, heat ½ cup heavy cream over medium heat until it’s just about to boil (small bubbles form at the edges).
2. Add Chocolate:
   • Remove from heat and add 1 cup semi-sweet chocolate chips.
   • Let sit for 2 minutes, then stir gently until smooth.
3. Incorporate Butter:
   • Stir in 1 tablespoon butter until fully melted and glossy.
4. Cool Ganache Slightly:
   • Let the mixture cool for 15 minutes to thicken.
5. Top the Cheesecake:
   • Spread the ganache over the chilled cheesecake evenly.
   • Refrigerate again until the ganache is set.