First make the vegetarian ground beef: Bring the broth to boil in a 3 quart saucepan.
Add the brown rice and lentils. Reduce heat, and simmer until soft or even mushy, about 1/2 hour. Add more water if necessary to prevent sticking.
To make pie: Preheat oven to 375 degrees.
Heat oil in a large skillet over medium heat. Add onion and bell pepper and sauté until soft, 3-4 minutes.
Add 2 ½ cups of lentil-rice mixture to skillet. Reduce heat to medium-low. Add chili powder, tomatoes, corn, and black olives to skillet. Cook, stirring occasionally until mixture is heated through.Add cheese to skillet. Stir until melted. Spoon mixture into a greased 8 x 8 inch pan, OR a greased 9x 13 inch pan.
Chop polenta and scatter over top of casserole. Sprinkle with queso fresco cheese if desired.
Bake for 30 minutes or until bubbly. Let stand 5 minutes before serving.
Serve as is or with salsa and chopped avocado.