I had mixed feelings about this cake. It was light and moist and had a great crumb, and when I first tasted it, I liked the flavors a lot. The next day, though, I felt like the cocoa taste was too pervasive. Full disclosure: I just use plain ol' cocoa, and not the good stuff; quite likely that made a difference. I did really like the peanut butter core. The cream cheese gave it a soft, almost cheesecake-like consistency. It was fun to try something new, and I might consider giving it another try with better cocoa.
Chocolate and Peanut Butter Bundt Cake
2/3 cup (6 1/3 ounces) peanut butter
1/3 cup cream cheese (Mary notes that she wasn't sure how many ounces are in 1/3 cup, so she used 4 ounces. I can't remember, but I think I followed her lead here.)
1 tablespoon butter
3 egg yolks
1 teaspoon vanilla
1/3 cup (2 1/3 ounces) sugar
2 tablespoons flour
Cake Batter Ingredients
1 3/4 cups (7 3/8 ounces) flour
1/2 teaspoon baking soda
1/2 teaspoon salt
3/4 cup cocoa powder
3/4 cup boiling water
3 ounces high quality bittersweet chocolate, chopped
3/4 cup sour cream
1 1/2 sticks butter
1 2/3 cups (11 5/8 ounces) brown sugar
2 teaspoons vanilla
Preheat the oven to 350F. Make the filling first. You'll put it into a pastry bag and give it a chance to chill in the fridge while you prep the cake batter.
For filling, beat peanut butter, cream cheese, and butter until combined. Add egg yolks, one at a time, and beat until combined. Mix in the vanilla, and scrape down the sides. (I've been using my new side-scraping Kitchen Aid blade, and it pretty much eliminates this step!) Pour in the sugar and flour and mix until just combined. Scoop the filling into a pastry bag fitted with a large tip. (The recipe says to use a plain tip, as opposed to a star tip, but I can't see what difference it makes. And for what it's worth, if you don't mind wasting a ziploc bag, you can just cut the corner off and use that to pipe the filling.) Place in the fridge until you're ready to use it.
Now the batter. In a medium bowl, whisk together the flour, baking soda, and salt. In another bowl, whisk the boiling water into the cocoa. Add the chopped chocolate and whisk until smooth. Mix in sour cream.
In a large mixing bowl, cream the butter and sugar until light and fluffy. Mix in the eggs, one at a time, and then beat in the vanilla. Beat in the dry ingredients and the cocoa mixture, alternating, beginning and ending with the flour. Each time, beat just until the ingredients are combined. Scrape down the sides and give it one final whirl.
Spray a bundt pan generously - no, REALLY - with cooking spray with flour (Pam with Flour or Baker's Joy). Spread a little less than half of the batter in the pan. Using the pastry bag, pipe a ring of peanut butter filling around the pan in the center. Keep away from the edges so the chocolate seals off the peanut butter. It makes for a better "reveal." You should use up all the peanut butter filling, so if you have to pipe a few rings around, that's just fine. Spread the rest of the batter on top and gently tap the pan on the counter to remove any air bubbles.
Bake until the top springs back when you press it - about 50-60 minutes. Mine took somewhere between 50-55 minutes. Let the cake cool on a wire rack for 5 minutes, then invert it, remove the pan, and let it cool completely.