1. Place dried chiles in medium bowl, and cover with 1 1/2 cups boiling water. Let stand 20 minutes, or until soft, pushing chiles under water occasionally. Let liquid cool until chiles are easy to handle.

2. Remove tough stems and seeds from rehydrated chiles, using soaking liquid to rinse away seeds. Coarsely chop chiles, and strain liquid to remove seeds. Set aside.

3. Heat oil in large Dutch oven over medium-high heat. Add bell pepper, onion, and garlic, and sear 1 to 2 minutes, or until beginning to brown. Add chiles with soaking liquid, tomatoes with juice, chili powder, brown sugar (if using), cumin, oregano, and 4 cups water. Season with salt and pepper, if desired. Cover, and simmer 30 minutes.

4. Remove pot from heat, and blend chiles and vegetables with immersion blender until smooth. Stir in eggplant chunks, then cover pot, and simmer 30 minutes over medium heat, or until eggplant is tender, stirring occasionally. Stir in masa harina, and season with salt and pepper, if desired.