Add olive oil to a large skillet over medium heat. Once hot, add chopped onion and cook until lightly browned.
1 medium onion, 1 Tablespoon olive oil
Add garlic. Stir until browned, then mix in ground beef and ground sausage. Cook, breaking up the pieces of meat with a wooden spoon, until browned.
2 cloves garlic, 1 pound ground beef, 1 pound Italian sausage
After browning the meat, stir the tomato sauce into the skillet. Season with Italian seasoning, then simmer on low for 30 minutes.
1 Tablespoon Italian seasoning, 8 cups tomato marinara sauce
Season with salt and pepper to taste, then remove from the heat.
salt and pepper to taste
Grease your slow cooker. Then, pour in 1 cup of the meat sauce you just prepared. You must always start with sauce at the bottom to prevent burning your lasagna.
Top the sauce with a layer of uncooked, oven-ready lasagna noodles. You will have to cut the lasagna noodles in order to fit them into the slow cooker.
1 pound uncooked lasagna noodles
In a bowl, add ricotta cheese with Parmesan cheese, parsley, salt, pepper, and eggs. Mix until completely combined.
32 ounces ricotta cheese, 4 eggs, ½ cup freshly chopped parsley, salt and pepper to taste
Add a ladle of the meat sauce over the noodles. Then, add about ¼ of the ricotta cheese mixture over the sauce. Top with a layer of mozzarella cheese and Parmesan cheese (again, ¼ the amount of each).
2 pounds low-moisture mozzarella cheese, 1 cup freshly grated Parmesan cheese
Repeat the layers in the same order three times.
Finish with a final layer of the remaining mozzarella and Parmesan.
Set the slow cooker to low. Cook for approximately 7 hours, or until the mixture is bubbly and the noodles have cooked through.
After cooking, set the slow cooker to warm. Allow the lasagna to rest. This enables the lasagna to set, which will make it easier to cut through without it falling apart.
Once ready to serve, cut the lasagna into squares with a knife. Use a metal spatula to serve. Serve with additional meat sauce and Parmesan cheese, if desired. It's great with a big salad!