Other than soups and fries?
I have a cookbook, The World of Vegetable Cookery, by Alex D. Hawkes. He has 2 recipes for Boniato.
1. Fritters -- bake unpeeled, peel and mash tender pulp. To 3 cups of pulp add 1 Tb cornstarch, 1 tsp baking powder, 1 tsp salt, 1/4 tsp nutmeg, 1/2 cup chopped raisins, 2 beaten eggs. Heat 1/2 cup melted lard and fry the boniato mixture by heaping tablespoons until browned on all sides. Drain, eat hot.
2. with Orange -- boil boniatos until tender, peel and mash. Mix in spices, pecans, raisins and tiny marshmallows. Cut slices from unpeeled oranges, put on a cookie sheet, spread mashed mixture on top. Bake in 325 degree oven 15 minutes.
He says that yucca is the same as cassava, usually served cooked with butter, salt and pepper, and lime or sour orange juice. He also gives a Cuban garlic sauce, just butter and oil heated with garlic for 15 minutes, sprinkled with parsley.