Make the Cake:

1. Prepare the Batter:
   • Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
   • In a large bowl, combine the cake mix, water, vegetable oil, and eggs. Beat until smooth and well combined.
2. Bake the Cake:
   • Divide the batter evenly between the prepared pans. Bake for 25–30 minutes, or until a toothpick inserted into the center comes out clean.
   • Let the cakes cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.

Make the Peanut Butter Filling:

3. Mix the Filling:
   • In a large mixing bowl, beat together the peanut butter, cream cheese, powdered sugar, and vanilla extract until smooth and creamy.

Assemble the Cake:

4. Layer the Cake:
   • Place one cooled cake layer on a serving plate. Spread the peanut butter filling evenly on top. Place the second cake layer on top, pressing gently to secure.

Make the Ganache:

5. Prepare the Ganache:
   • In a small saucepan, melt the butter over low heat. Add the chocolate chips and heavy cream, stirring until smooth and glossy. Remove from heat and let cool slightly.
6. Top the Cake:
   • Pour the ganache over the top of the assembled cake, allowing it to drip down the sides. Smooth the ganache with a spatula if needed.

Serve:

7. Chill and Slice:
   • Let the cake sit at room temperature for 15–20 minutes, or refrigerate for 30 minutes for the ganache to set. Slice and serve!