Saute onion in olive oil, until well browned. Add garlic, cumin, cinnamon and chiles. Saute for 3 minutes. Add tomatoes, squash, salt and broth. Lower heat, cover and simmer for 1 hour. Add mushrooms and cilantro and simmer for 5 minutes. Sift together cornmeal, flour, baking powder, salt and sugar. Beat together egg and milk. Stir into dry mixture. Add butter and stir until smooth. Add to stew by the teaspoonfuls and simmer for 20 minutes. Serve.