- 1 tablespoon cocoa powder
- 1 3/4 cups white sugar
- 3/4 cup vegetable oil
- 3 eggs
- 1/4 cup mashed sweet potatoes
- 1 teaspoon vanilla extract
- 2 cups all-purpose flour
- 1/2 cup cocoa powder
- 1 teaspoon baking soda
- 1 teaspoon ground cinnamon
- 1 teaspoon salt
- 1/2 cup quick-cooking oats
- 3 cups peeled, cored, and cubed Granny Smith apples
- 1 cup chopped walnuts
- Preheat oven to 300 degrees F (150 degrees C). Grease a 9×5-inch loaf pan and dust with 1 tablespoon cocoa powder.
- Whisk sugar and oil together in a large bowl until smooth. Beat eggs, 1 at a time, into sugar-oil mixture, beating thoroughly before adding the next egg. Beat mashed sweet potato and vanilla extract into sugar-egg mixture until smooth.
- Sift flour, 1/2 cup cocoa powder, baking soda, cinnamon, and salt together in a separate bowl. Sprinkle oats over flour mixture. Stir flour mixture, 2 to 3 tablespoons at a time, into sweet potato mixture until batter is just mixed; fold in apples and walnuts. Spread batter into the prepared loaf pan.
- Bake in the preheated oven for 70 minutes. Increase temperature to 350 degrees F (175 degrees C) and bake until a toothpick inserted in the center comes out nearly clean, 20 to 30 minutes more.