Step 1: Cook lasagna noodles according to package instructions in a large pot of salted boiling water until al dente. Drain well and set aside, perhaps laying them out to prevent sticking.
Step 2: In a large skillet, melt 1/2 cup of butter over medium heat. Add 4 cloves of minced garlic and cook for 1-2 minutes until fragrant, but not browned.
Step 3: Add the peeled and deveined shrimp to the skillet. Cook for about 2-3 minutes per side, just until they turn pink and opaque. Remove the shrimp from the skillet and set aside in a bowl.
Step 4: In the same skillet, melt the remaining 1/2 cup of butter over medium heat. Add the other 4 cloves of minced garlic and cook for another 1-2 minutes until fragrant.
Step 5: Stir in the 1/4 cup of flour. Whisk constantly for about 1 minute to create a roux.
Step 6: Gradually whisk in the 2 cups of milk, pouring slowly and whisking constantly to prevent lumps. Continue whisking as the sauce heats and thickens until smooth.
Step 7: Remove the skillet from the heat. Stir in the Parmesan cheese until completely melted and the sauce is smooth. Season generously with salt and pepper. Stir in 1/4 cup of the chopped fresh parsley.
Step 8: Add the remaining 1/4 cup of chopped parsley and the tablespoon of lemon juice to the cooked shrimp. Season with salt and pepper and toss gently to coat.
Step 9: Preheat your oven to 375°F (190°C).
Step 10: To assemble, spread a thin layer of the creamy garlic butter sauce on the bottom of a 9x13 inch baking dish.
Step 11: Arrange a layer of cooked lasagna noodles over the sauce, overlapping slightly if needed.
Step 12: Spread another layer of creamy sauce over the noodles. Scatter half of the seasoned shrimp over the sauce and sprinkle with a good amount of mozzarella cheese.
Step 13: Repeat the layers: noodles, sauce, remaining shrimp, and more mozzarella.
Step 14: Finish with a final layer of noodles, spread the rest of the creamy sauce over the top, and sprinkle with the last of the mozzarella cheese.
Step 15: Cover the baking dish tightly with foil. Bake in the preheated oven for 25 minutes.
Step 16: Carefully remove the foil. Bake for an additional 10 minutes, or until the cheese is golden brown and bubbly.
Step 17: Remove from the oven and let it cool for 5-10 minutes before slicing and serving to allow the layers to set.