Prepare the nopales: Cut the nopales into strips. (See my other recipes for tips on cooking nopales without them getting slimy.) Rinse well and let them drain.

Prepare the shrimp: Clean the dried shrimp by removing the eyes and discarding them, as they can be bitter. Separate the heads. Toast the shrimp on both sides, watching carefully so they don't burn. You can cook the heads in about 2 cups (1/2 liter) of water to extract maximum flavor, then strain the liquid and discard the heads.

Once the shrimp are toasted on both sides, let them cool. Blend them dry in a blender or food processor until you get a fine powder. Set aside.

Prepare the sauce: Toast the chiles on both sides, removing seeds and veins. Also roast the tomatoes, onion, and garlic. Soak the chiles in the shrimp head broth.

Once the chiles are soaked, blend them well with the onion, tomatoes, garlic, and cilantro until you have a smooth sauce. You can heat 2 tablespoons of oil in a large pot, sauté the sauce briefly, and set aside for the patties.

For the patties: Separate the egg whites from the yolks. Beat the egg whites until stiff peaks form. Once firm, add the yolks one at a time, beating after each addition. Gradually fold in the rice flour, then the shrimp powder, mixing until smooth.

In a skillet with enough hot oil, drop about 1 1/2 to 2 inch (4-5 cm) portions of the batter to form patties. Fry each patty on both sides until golden, then drain on paper towels.

Add all the patties, bouillon cubes, and nopales to the sauce. Bring to a simmer for a few minutes. Taste and add more salt if needed, though it's usually not necessary.

Serve 2 or 3 patties per person with some broth and nopales. These go great with rice or refried beans.