Makes about 18-20I used a combination of Martha's One Bowl Chocolate Cupcakes and her Peanut Butter Cupcakes, halving each of the original recipes listed below.
One Bowl Chocolate Cupcakes
3/4 cup unsweetened cocoa powder
1 1/2 cups all-purpose flour
1 1/2 cups sugar
1 1/2 teaspoons baking soda
3/4 teaspoon baking powder
3/4 teaspoon salt
2 large eggs
3/4 cup warm water
3/4 cup buttermilk
3 tablespoons safflower oil
1 teaspoon pure vanilla extract
1. Preheat oven to 350 degrees. Line standard muffin tins with paper liners; set aside. Sift together cocoa powder, flour, sugar, baking soda, baking powder, and salt into a large bowl. Add eggs, warm water, buttermilk, oil, and vanilla, and mix until smooth, about 3 minutes. Scrape down the sides and bottom of bowl to assure batter is well mixed.
2. Divide batter evenly among muffin cups, filling each 2/3 full. Bake until tops spring back when touched, about 20 minutes, rotating pan once if needed. Transfer to a wire rack; let cool completely.
Peanut Butter Cupcakes
1 3/4 cups all-purpose flour
3/4 tablespoon baking powder
1/2 teaspoon salt
1/4 teaspoon baking soda
6 ounces (1 1/2 sticks) unsalted butter, softened
1 1/3 cups sugar
2/3 cup natural, creamy peanut butter
3 large eggs
1/2 cup sour cream
1/2 teaspoon pure vanilla extract
1. Preheat oven to 350 degrees. Line standard muffin tins with paper liners. Whisk dry ingredients in a large bowl. Cream butter and sugar with a mixer until light and fluffy. Add peanut butter; cream until smooth. Add eggs, 1 at a time, beating after each addition.
2. Reduce speed to low. Mix sour cream and vanilla in a bowl. Add dry ingredients to butter mixture in 3 additions, alternating with sour cream mixture and ending with dry. Scrape sides of bowl. Divide batter among muffin cups, filling each 2/3 full.
3. Bake cupcakes until testers inserted into centers come out clean, about 20 minutes. Let cool in tins on wire racks. Cupcakes will keep, covered, for up to 3 days.
*Note: When combining the two batters, I put a heaping cookie scoop (about 1/4 of a cup) of the peanut butter into the cupcake papers first, and then added a scoop of the chocolate batter on top. I used a toothpick to swirl the batters together for the marbling effect.
Peanut Butter Frosting
Makes about 3 cups
From Martha Stewart Living February issue or MarthaStewart.com
6 ounces cream cheese
1/3 cup confectioners' sugar
1/2 teaspoon salt
1 cup creamy peanut butter (not natural)
1/2 teaspoon pure vanilla extract
1/2 cup heavy cream
About 20 mini Peanut Butter Cup candies (optional)
1. Beat cream cheese and confectioners' sugar with a mixer on medium speed. Add salt, then peanut butter, then vanilla. Whisk cream until soft peaks form, and then fold into peanut butter mixture. Use immediately, or cover and refrigerate for up to 2 days. (Bring to room temperature, and beat on low speed until smooth before using.)
2. Pipe or spread frosting onto cooled cupcakes. Top with unwrapped candy, if using.
I've been on a cupcake kick lately. It all started when I got my new Martha Stewart Living magazine in the mail.. Cupcakes featured on the front. 15 cupcake recipes inside! I wanted to make them RIGHT away!
But I had been sick the past few days, and I wasn't feeling quite up to coughing all over my tasty treats. So I held off.. A few days later, my boyfriend and I decided to have an "indoor picnic" on MLK day since we both had the day off. I was in charge of bringing the desserts.. so of course I picked cupcakes! He is a peanut butter fanatic.. I mean, he'll literally eat spoonfuls of peanut butter out of the jar and call it dinner. So I thought it would be perfect to make the Peanut Butter cupcakes with Peanut Butter icing from Martha for him. It just seemed like a little too much peanut butter for me.. So I decided to mix it up a bit and make the peanut butter AND the chocolate cupcakes and marble them together! It'd be like a Reese's Peanut Butter Cup-cake! I had the majority of what I needed already, so I picked up the few remaining ingredients, and hoped by the time I was ready to bake, my coughing would have subsided. It didn't... But I figured, I'm making these for just me and my boyfriend.. I'm already sick, and if he's gonna get sick, he's probably already on his way there from being around me for the past week.. So I set off on my baking adventure!First I made the "One Bowl Chocolate Cupcakes" (Pg 148 of the Feb2009 issue of Living Magazine). I halved the recipe since I was making 2 separate batters. They were incredibly easy to make. They really were a One Bowl recipe. The only thing I thought was a little odd was that the batter was kind of runny.. Just thinner than what boxed cakemix looks like. Other than that it looked fine! On to the peanut butter (Pg 148-149 of the Feb2009 issue of Living Magazine or at marthastewart.com)! This wasn't a one bowl recipe, but it was still simple. I halved this one as well. It came out as a beautiful batter.
The only problem was that it was the complete opposite of my chocolate batter. Where the chocolate batter was slightly runny, my peanut butter batter was light and fluffy.. I started to doubt that marbling them would work out.. It was a little touch and go while I was marbling them. I had to keep digging to the bottom with my toothpick to get the batters to mix, but I ended up getting a pretty decent swirl on them. I just hoped they would bake evenly. They both had the same cooking time and temp in the recipes but I was slightly worried.They ended up coming out pretty well! They didn't sink, they didn't overflow--they came out just right! And even had a nice swirl to them!
Now it was on to icing them. I used the peanut butter icing from the magazine as well (pg 149 or marthastewart.com).
It was a cream cheese based frosting, made fluffy by the addition of whipped heavy cream. My hope going into it was that it would come out almost as a stiff buttercream, because I really wanted to swirl the icing up into a peak and drizzle melted chocolate down over the top to make a really beautiful cupcake. Unfortunately, this recipe didn't lend itself well to that idea. So I stuck with just icing them and sticking a mini peanut butter cup on top instead. With my cupcakes in hand, I headed off to my boyfriend's house for our "indoor picnic". 
We couldn't wait until dinner was actually done to try them, so we had a little taste of dessert as an appetizer. The cupcakes themselves were moist, but with all the swirling I had to do with my toothpick, it made the wrapper hard to pull away from the cupcake. That was Flaw #1. Inside they were pretty though. They weren't the greatest marbling job, but you could definitely see the swirl. Flaw #2 for me was that the cupcakes, while being moist and pretty, really didn't taste fantastic. They were neither chocolatey nor peanut buttery. They were just kind of sweet with no real distinct flavor. Flaw #3 was my boyfriend's opinion, which I whole heartedly agree with. The icing wasn't nearly sweet enough. 
It was peanut butter alright, but more than that, it was overwhelmingly cream cheese flavored. It had a definite bite to it. It could use a bit more than the 1/3 of a cup of confectioners' sugar it called for. All in all, they were alright cupcakes. Nothing that you would find on the shelves of a bakery, but not a total disaster. Maybe next time, I'll try them individually, rather than mixed, and I'll add a little more sugar to the icing.See more pictures at my Flickr Page!
