Preheat oven to 350 degrees Fahrenheit, grease and flour a 10-inch bundt pan and set aside.
Whisk together your flour, baking powder, baking soda and salt in a medium bowl.
In a stand mixer beat butter on medium speed to soften, slowly add the sugar and beat until combined (and no longer granulated). Add in the eggs one at a time.
Beat in sour cream and vanilla until a nice batter forms.
Add the flour mixture and milk alternatively until just combined (about two minutes).
Transfer half of the batter to a bowl, stir in the melted chocolate. To the other half of the batter stir in the creamy peanut butter
Alternatively drop spoonfuls of the two batters into your pan. Only fill the pan 3/4 of the way, use the rest of the batter to make a loaf cake! Use a knife to swirl the batters together gently.
Bake for 50-60 minutes until a toothpick comes out clean. Cool the cake in the pan for 15 minutes and then flip onto a cake plate.