Sweet Potato Corn Bread

1 large sweet potato (to make 2 cups pulp)
1/4 pound butter
4 eggs, beaten
1/2 cup brown sugar
1/2 teaspoon baking soda
1 teaspoon salt
1 teaspoon cinnamon
1 cup yogurt
2 cups finely ground white cornmeal
1/2 cup sultana raisins (optional)
1/2 cup pecans (optional)

Bake or boil the sweet potato in its skin; when cool enough to handle, peel it and pur