Preheat the oven to 350 degrees.
Grease a 10-cup bundt pan.
In a large mixing bowl combine the cake mix, brownie mix, egg, water, and oil. Check what ingredients your particular mixes call for as it might be a little different than what I listed. Just make sure to add the listed ingredients for both mixes that they call for on the back of the box.
Pour half of the batter into the prepared bundt pan.
In a medium mixing bowl combine the cream cheese, sugar, egg, and peanut butter until smooth.
Add spoonfuls of the peanut butter mixture all around the bottom layer of the batter.
Top the peanut butter mixture with the rest of the batter.
Transfer your bundt pan to a baking sheet and bake for 50-60 minutes, or until a toothpick inserted in the center comes out clean.
Cool the cake for 10 minutes before inverting it onto a wire rack to cool completely.
Once cool heat up the heavy whipping cream in the microwave for 30 seconds to a minute, you want the cream hot.
To the cream add the chocolate chips and let sit for 5 minutes.
Stir the chips and cream together until melted and shiny.
Drizzle the chocolate ganache all over the top of the cake.
In a small microwave-safe bowl melt your peanut butter for 20 seconds.
Drizzle the peanut butter over the top of the cake.
Add chopped or whole mini reeses cups.