A Native American expression, “three sisters” refers to the practice of growing beans, corn, and squash together. This filling casserole can be frozen for an upcoming party or made fresh for dinner. Serve with Pumpkin Seed Pesto.
1. To make Polenta Topping: Whisk together cornmeal, chili powder, salt, and 4½ cups water in double boiler, or in large metal bowl over barely simmering water. Cook 40 minutes, or until polenta is thick and stiff, stirring 3 or 4 times. Remove from heat.
2. To make Filling: Preheat oven to 375°F. Heat 2 Tbs. oil in large saucepan over medium heat. Add onion, and cook 7 minutes, or until softened, stirring often. Add bell pepper, and cook 5 minutes more, stirring often.
3. Stir in squash, tomatoes, garlic, coriander, and cumin. Cook 5 minutes, stirring occasionally. Stir in ½ cup water and salt. Bring mixture to a boil. Reduce heat to medium low, and simmer, partially covered, 10 to 15 minutes, or until squash is tender. Stir in beans and corn, and cook 5 minutes, or until slightly thickened, stirring occasionally.
4. Coat 8- x 11-inch baking dish with cooking spray. Spread 2 cups polenta over bottom of prepared dish. Spoon squash mixture over polenta. Smooth remaining polenta (about 2½ cups) over top.
5. Score casserole into 6 squares with knife. Brush top with remaining 1 Tbs. oil. Bake 30 minutes, or until heated through and top is lightly browned.