This is a cake made of magic. Because as we all know, peanut butter and chocolate are magic.
- Prepare brownies in a 9-inch round baking dish according to package instructions. Remove from oven and allow to cool.
- While brownie cools, make the peanut butter mousse. Beat together cream cheese and half of the powdered sugar until creamy. Scrape the bowl and beat in remaining powdered sugar. Add in peanut butter and vanilla extract, beat until creamy. Finally, pour in heavy whipping cream and beat on medium speed until thick.
- Top the cooled brownie with Mini Reese's Peanut Butter Cups. Gently spread peanut butter mousse over it. Refrigerate while you make the next layer.
- For the chocolate mousse, beat together cream cheese and powdered sugar until creamy. Add in vanilla extract and heavy whipping cream, beating on medium speed until thick. Gently fold in melted chocolate. Don't fold in completely, as you want it to look marbled.
- Spread mixture over cooled peanut butter layer. Refrigerate again while you make the last layer.
- To make the chocolate ganache, pour heavy cream over chocolate chips in a microwave-safe bowl. Microwave on 30 second intervals, stirring each time, until combined and smooth.
- Pour ganache over cake. You can either refrigerate to set chocolate ganache, or serve while chocolate ganache is slightly warm. Enjoy!