Preheat the oven to 350 degrees F. Lightly grease a mixing bowl and baking sheet. In a mixing bowl, whisk the yeast and water together, until the yeast dissolves. Add in the sugar, salt, pepper, and butter. Mix well and let rest for 15 minutes. Stir in the eggs and sweet potatoes. Mix the flour and raisins together. Fold in the flour, 1/2 cup at a time, working with your hands until all the flour is incorporated. Form the dough into a small ball and sprinkle the dough with the remaining tablespoon of flour. Place the dough in a lightly oiled bowl, turning the dough once to cover with the oil. Cover the bowl with a clean cloth and let rise until doubled in size, about 1 1/2 hours. Punch the dough down and roll into an oval loaf about 8 inches by 3 inches. Place the loaf in the center of the prepared baking sheet. Cover and let rise until double in size, about 45 minutes. Bake the bread for about 40 minutes, or until golden. Remove the bread from the oven and transfer to a wire baking sheet and let cool. Slice the bread and serve with butter.