If you can't find sweet potato puree, make your own using either baked or canned whole sweet potatoes. Puree in a processor until completely smooth.
- 4 tablespoons (1/2 stick) unsalted butter
- 2/3 cup natural unsweetened cocoa powder
- 1/2 cup whole-wheat pastry flour
- 1/4 teaspoon baking powder
- 1/4 teaspoon salt
- 1 cup sugar
- 2/3 cup sweet-potato puree
- 1 large egg
- 1 1/2 teaspoons vanilla extract
- 1/4 teaspoon instant coffee powder
Heat oven to 350 degrees. Butter an 8-inch square pan; set aside. In a medium saucepan over low heat, melt butter. Remove pan from heat, and stir in cocoa. Let cool slightly.
Meanwhile, in a small bowl, whisk together flour, baking powder, and salt.
Stir in sugar and sweet-potato puree, then egg. In a small bowl, stir together vanilla and coffee until coffee is dissolved; add to cocoa mixture.
Add flour mixture to cocoa mixture and stir until no traces of flour remain. Spoon into prepared pan; smooth the top. Bake until surface of brownies looks barely dry and an inserted knife comes out with a few moist crumbs, about 20 minutes. Cool to room temperature before serving.