Simmer (covered in watter) tomatillos about 10 minutes, or until they soften. Cool, place in food processor with 1/2 cup of cooking liquid. Add serranos and cilantro and puree. Saute onion & garlic in oil, 5 minutes. Add tomatillo puree, salt & sugar. Simmer 10 minutes until thickened, set aside. Steam rice until done. Sauteonion & green pepper in oil until softened, 10 minutes. Add garlic, salt and herbs, cook 2 mintues. Season with salt and pepper, add rice, green sauce and 1 cup of cheese. Remove from heat. Preheat oven to 350. Spoon rice mixture into baking pan, smooth flat. Sprinkle to pwith remaining cheese. Cover with foil, bake 30 mintues, remove foil, brown top for a few minutes, then serve.