*VEGETARIAN OPTION 1 cup of chopped eggplant with 1/2 tsp HOT SMOKED PAPRIKA
Rinse chiles, then cover with cold water in a bowl and soak, weighted with a sieve (to keep submerged), until completely rehydrated (most will turn a brighter red), about 6 hours. Do not drain chiles.
Remove chiles , one at a time, from soaking liquid and cut a slit down one side with scissors and let interior liquid and loose seeds drain out. Carefully cut out seedpod, leaving stem intact and letting any easily loosened seeds fall into sieve, then discard all the seeds.
Arrange seeded chiles, cut sides up, in 1 layer in a 13- by 9- by 2-inch (3-quart) baking dish.
Reserve 1 cup chile-soaking liquid for sauce.
Purée tomatoes, including juice from can, in a blender with reserved soaking water, ground chile seeds, and 1/2 teaspoon salt until smooth, then transfer to a 3-quart heavy saucepan and boil, stirring occasionally, until sauce is thickened slightly and reduced to about 2 cups, 5 to 7 minutes.
Peel potatoes and cut into cubes and cook 6 to 8 minutes in boiling water. Drain in a colander and rinse under cold water to stop cooking.
Stir together potatoes, chorizo, cheese, and 1/4 teaspoon salt in a bowl, then fill chiles generously with stuffing (about 1/2 cup each; slit will not close over it). Pour sauce around (not over) chiles, then cover dish with foil and bake until sauce is bubbling all over, 35 to 45 minutes.
Serve with rice.