Peanut Butter Cupcakes with Chocolate Satin Frosting

Joy of Cooking, p. 962

1 1/4 cups all-purpose flour
3/4 cup packed light or dark brown sugar
1 1/2 tsp baking powder
1/2 tsp salt
3/4 cup milk
1/3 cup creamy peanut butter
1 large egg
1 Tbsp unsalted butter, softened
1 Tbsp vegetable oil
1 tsp vanilla
3/4 cup semisweet chocolate chips (optional)

Preheat oven to 350 F. Line muffin pans with paper liners. Combine all ingredients and mix until smooth. Fill the muffin cups about two-thirds full. Bake until a toothpick inserted in the center of a cupcake comes out clean, 25-30 minutes. Remove from the pan and let cool completely on a rack before frosting.

Chocolate Satin Frosting, Joy of Cooking p. 1004
Break or cut into pieces.
6 oz unsweetened chocolate
Bring to a boil in a small saucepan
1 cup heavy cream
Remove from heat and add chocolate pieces, without stirring. Cover and set aside for 10 minutes. Add:
1 1/2 cups sugar
6 tablespoons butter, cut into pieces
1 teaspoon vanilla
Mix until smooth. Transfer to bowl. Refrigerate until thickened to desired consistency.