I have several baking books by Martha Stewart and I'm irresistibly drawn to the pictures of the recipes. They always look so good. I've tried a number of her recipes and they've almost always come out. So then I wonder why I don't use her recipe books more often. But once I flip through them in their entirety, I realize I'm only up to making maybe half of the recipes. The other half is too fancy and involved. Very Martha in looks but few people have that kind of time to make gorgeous concoctions. And even if I had the time, to be honest, I don't think I'd go to the bother. I tend to err on the side of simplicity and taste. One more reason why I'm more of a brownie or cookie baker rather than a wedding cake decorator.
In any case, this recipe couldn't have been simpler to make. I mixed the chocolate batter by hand and used a hand mixer to blend the peanut butter filling ingredients. For the filling, make sure your butter is softened to room temperature and mix it well with the peanut butter so they end up well blended and the same creamy texture with no lumps. I ended up with enough batter to make fill 12 muffin cups and 1 ramekin. Don't try to force them into 12 muffin cups if you have too much batter or they might overflow.
I discovered the hard way that you need to marbleize or swirl these so that you have more of the chocolate covering the peanut butter on top. Otherwise the peanut butter batter will puff up and spill over the top of the cupcake liner. When you take them out of the oven, they deflate and look sloppy, especially when you try taking them out out of the muffin cavity. Mine don't look close to Martha's version - sigh. So cover the peanut butter batter with the chocolate and only allow a small part of the peanut butter batter to show through the top. Once you get past the sloppy appearace, taste-wise, these are like eating a Reese's peanut butter cup in cupcake form. Judge the baking time on whether the chocolate part is done (with a few moist crumbs clinging to a tester) and not when the peanut butter part is "done" because the peanut butter batter isn't going to bake like the chocolate batter. It'll stay creamy and it's supposed to. Don't overbake or the chocolate cupcake part will be dry and not fudgy,
2/3 cup all-purpose flour
½ teaspoon baking powder
¼ teaspoon salt
½ cup (1 stick) unsalted butter, cut into small pieces
4 ounces semisweet chocolate, coarsely chopped
2 ounces unsweetened chocolate, coarsely chopped
¾ cup granulated sugar
3 large eggs
2 teaspoons vanilla extract
Peanut Butter Filling
4 tablespoons unsalted butter
½ cup confectioners’ sugar, sifted
¾ cup smooth peanut butter
¼ teaspoon salt
½ teaspoon vanilla extract
1. Preheat oven to 325⁰F. Line a muffin tin with paper liners. Whisk together flour, baking powder and salt. Put butter and chocolate in the top half of a double boiler over hot, simmering water; stir until melted. Remove from heat and let cool slightly.
2. Whisk granulated sugar into cooled chocolate mixture. Add eggs and whisk until mixture is smooth. Stir in vanilla. Add flour mixture; stir until well incorporated.
3. Make the peanut butter filling: stir together all filling ingredients until smooth.
4. Spoon 2 tablespoons chocolate batter into each lined cup, followed by 1 tablespoon peanut butter filling. Repeat with additional tablespoon batter and top with 1 teaspoon filling. Swirl top of cupcake batter and filling with a wooden skewer or toothpick.
5. Bake, rotating halfway through, until a cake tester inserted in the centers comes out with only a few moist crumbs attached, about 40 minutes. Transfer to a wire rack to cool completely before removing cupcakes.
Cupcakes can be stored up to 3 days at room temperature in airtight containers.