Preheat the oven to 350°F. Spray a 10-inch bundt pan with nonstick cooking spray.
In a large bowl, whisk together sugar, flour, cocoa powder, baking soda, baking powder, and salt. Set aside.
In a separate bowl, whisk together the butter, eggs, sour cream, and buttermilk.
Pour the wet ingredients into the dry ingredients and stir to combine. Add the coffee, and whisk until the batter is completely combined. Set aside.
Peanut Butter Filling
In a large bowl, add peanut butter, cream cheese, and brown sugar. Mix with a hand mixer on medium until creamy (4-5 minutes).
Add the egg and vanilla and continue to mix until combined.
Add the flour and salt. Mix on low until fully incorporated.
Assembly
Dust the bundt pan with the remaining tablespoon of cocoa powder.
Scrape ⅔ of the cake batter into the prepared bundt pan. Using a 1½ tablespoon scoop (or a spoon), scoop the peanut butter filling in the center. Be sure to not press on the peanut butter filling too hard so it doesn't sink too far into the cake batter. Top with the remaining cake batter. Use a spatula or wooden spoon to smooth the top, if necessary.
Bake for 50-55 minutes, or until a toothpick inserted in the center of the cake comes out clean. Cool in the cake pan for 15 minutes. Then invert the cake onto a serving plate and let it cool completely (about an hour) before adding the glaze.
Chocolate Ganache
Place heavy whipping cream in a medium microwave-safe bowl and heat for about 45 seconds to a minute. You want the cream to be just boiling.
Carefully pour chocolate morsels into cream.
Let sit for 5 minutes (to melt the chocolate). Whisk the chocolate and cream until shiny and smooth, about 1 minute.
Pour over cooled cake.
Peanut Butter Topping
Place heavy whipping cream in a large microwave-safe bowl and heat for about 45 seconds to a minute. You want the cream to be just boiling.
Add peanut butter and let sit for a few minutes to soften the peanut butter. Add confectioners' sugar and whisk to combine. (It should be thick, but pourable.) Pour over chocolate ganache.
Top with chopped peanut butter cups.
Allow the cake to set about 10 minutes before serving.