To make sauce: In a blender or food processor, pulse tomatillos, jalapeños and 1 1/2 cups cold water just until chunky.
Add onion, cilantro, salt, chiles, lettuce, green onions, and garlic.
Purée about 2 minutes or until smooth.
To make lasagna: Preheat oven to 350°F.
In a 13-inch by 9-inch by 2-inch baking dish, spread 1 cup of the sauce.
Layer one third of the shrimp over the sauce.
Place 3 lasagna noodles over the shrimp. Noodles should not overlap or touch side of pan since they will expand when baked.
Combine cheeses and sprinkle about 2 cups over noodles.
Repeat layering sauce, shrimp, noodles, and cheese two more times.
Top with remaining 3 lasagna noodles and spread remaining sauce over noodles.
Sprinkle with remaining cheese.
Cover with aluminum foil and bake for 30 minutes.
Remove foil and bake 10 to 15 minutes or until hot and bubbly.
Allow to rest for 10 minutes. Cut into squares and serve immediately.