Preparation Sauté beef in heavy large pot over medium-high heat until no longer pink, breaking up meat with back of fork, about 3 minutes. Add chili powder and cumin; stir 1 minute. Add salsa, beans and broth. Simmer until mixture thickens, about 10 minutes. Mix in 1/4 cup cilantro; season with salt and pepper. Oil 13x9x2-inch glass baking dish. Place half of polenta in dish. Top with sauce and 1 1/2 cups cheese, then remaining polenta, cheese and cilantro. (Can be made 1 day ahead. Cover with foil; chill.) Preheat oven to 350°F. Bake freshly assembled pie, uncovered, until heated through and sauce bubbles, about 35 minutes, or bake refrigerated pie, covered, 20 minutes, then uncover and bake until heated through, about 35 minutes.
Preparation Sauté beef in heavy large pot over medium-high heat until no longer pink, breaking up meat with back of fork, about 3 minutes. Add chili powder and cumin; stir 1 minute. Add salsa, beans and broth. Simmer until mixture thickens, about 10 minutes. Mix in 1/4 cup cilantro; season with salt and pepper. Oil 13x9x2-inch glass baking dish. Place half of polenta in dish. Top with sauce and 1 1/2 cups cheese, then remaining polenta, cheese and cilantro. (Can be made 1 day ahead. Cover with foil; chill.) Preheat oven to 350°F. Bake freshly assembled pie, uncovered, until heated through and sauce bubbles, about 35 minutes, or bake refrigerated pie, covered, 20 minutes, then uncover and bake until heated through, about 35 minutes.