Tex-Mex Chili Gravy

4 dried red New Mexico chiles*
8 dried red ancho chiles*
1 pound ground beef
4 cups beef stock
1 medium onion, finely chopped
2 garlic cloves, minced
2 tablespoons bacon drippings (optional)
2 teaspoons cumin seeds, toasted and ground
1/2 teaspoon Mexican oregano
1/2 teaspoon salt
1 tablespoon Masa Harina