Bring a large pot of salted water to a boil. Cook your lasagna sheets according to your package’s directions. I cooked mine for about 8 minutes. (I always like to cook them until very al dente since they’re going to cook a tad bit longer in the oven with the lasagna.) Set the sheets aside, being sure to keep them separated, as they get super sticky as they dry.
Preheat your oven to 325 degrees F. In a medium saucepan, heat the olive oil over medium heat. When the oil is hot, add the ground lamb and sprinkle with about a 1/2 of salt. Break up the lamb into crumbles with a wooden spoon and cook until the meat is browned. Pour in the sauce and mix until the meat is thoroughly coated. Bring the sauce to a simmer and then immediately reduce the heat to low. Cover the pot and allow the sauce to simmer for about an hour.
To assemble the lasagna, place the first layer of lasagna noodles side by side in your 13” x 9” x 2.5” baking dish. Spread out about a quarter cup of sauce and top with a few dollops of ricotta and a handful of shredded mozzarella. Continue to build the layers until you’ve reached the top (I made about 5 layers). Top the lasagna with more sauce, more cheese and a few dollops of the crescenza cheese.
Transfer to the oven to bake for 30 minutes; you’ll know the lasagna is ready when the cheese is melty and sauce is bubbling.