Step 1Remove the papery outer husks of the tomatillos and the stem and seeds from the jalapeno. Place the tomatillos and jalapeno in a pan of water, bring to a boil and simmer, uncovered, until the tomatillos are softened, about 7 minutes. Drain.
Step 2Place the cooked tomatillos and jalapeno, the garlic and the cilantro in a blender and puree until smooth.
Step 3Heat the oil in a saucepan. Add the tomatillo mixture and cook 5 to 7 minutes. Season with salt and chicken stock base. Makes 1 1/2 cups.
Step 1Peel the shrimp and cut into one-third- to one-half-inch pieces.
Step 2Heat the oil in a skillet. Add the onion and bell pepper and cook until tender, about 7 minutes. Add the tomatoes and simmer until cooked through, about 5 minutes. Add the shrimp pieces and cook until they turn pink, about 3 minutes. Remove from heat and set aside.
Step 3Heat a griddle until very hot. Oil it lightly. Add the nopales in a single layer, in batches, and cook over high heat for 2 minutes, then turn and cook 2 more minutes on the other side.
Step 4Place 1 nopal on each of 4 ovenproof plates. Cover with one-fourth of the shrimp mixture. Top each shrimp layer with another nopal. Pour salsa verde over each, then sprinkle with cheese. Place under the broiler until the cheese is melted, about 1 minute. Serve immediately.