Brown meat: In a large skillet, brown the ground beef and sausage over medium-high heat, breaking the meat apart into pieces with a wooden spoon. When cooked through, remove the grease.
(Optional) Add meat to a food processor and pulse just 3-4 times until it’s broken up into very small pieces. Remove to a bowl.
Sauté Veggies: In the same skillet over medium-high heat, add olive oil. When oil is hot, add the garlic, stirring constantly for 30 seconds. Add the onion, spinach and bell pepper. Continue cooking on medium-high heat until the vegetables are softened –about 2-3 minutes.
Remove from heat and transfer them to the same food processor. Pulse several times until they’re nearly pureed. Return mixture to the skillet.
Add Tomato sauce and tomato paste and stir to combine. Add the diced tomatoes, Italian seasoning, and salt and pepper to taste. Stir. Cover and allow the sauce to simmer for about 20-30 minutes on low heat, stirring occasionally. Right before using the red sauce in the lasagna, stir in the reserved crumbled ground beef and sausage, and fresh basil.
Cook Pasta: While the red sauce simmers boil the lasagna noodles for half the time suggested on the box. Drain into a large colander and sprinkle them with a tiny bit of olive oil to keep them from sticking together. (You can skip this step if you are using no-boil noodles).
For the White Sauce: (Can be made in advance).
Add the butter to a medium size saucepan or large skillet. Over medium heat. Once melted, add the flour, stirring constantly to combine 2 minutes. Gradually add in the milk, whisking until smooth. Season with salt and pepper.
Cook over medium heat, whisking often so it doesn’t burn on the bottom, until it thickens-- about 5-7 minutes.
Preheat the oven to 350 degrees. Lightly grease a 9X13-inch baking pan with cooking spray. Keep in mind that there will be 3 layers of lasagna, so mentally split the sauces into thirds as you layer them to make sure you have enough at the end.
Layer: Start by layering the bottom of your greased pan with 3 lasagna noodles. Spread the red sauce over the noodles, followed by the white sauce, Parmesan and mozzarella cheeses, spreading all to the edges. Top with another layer of noodles, then red sauce, white sauce, parmesan and mozzarella cheeses.
Repeat: Add the final layer of noodles, then red sauce, white sauce and cheeses.
Bake for 30 minutes. Allow the lasagna to sit for 15-20 minutes before serving.
Make Ahead Instructions: You can make the white sauce and red sauce in advance. You could also boil the noodles in advance. If you want to assemble the lasagna before baking it, make it according to the directions, cover it with plastic wrap, and then tinfoil and refrigerate it for up to 2 days.Freezing Instructions:
Baked: Assemble and bake lasagna as instructed (using uncooked regular noodles or no-boil noodles). Allow to cool completely. Cover really well with a layer of plastic wrap and then a double layer of aluminum foil and freeze for up to 2 months. When ready to eat, you can thaw in the fridge for 24 hours, as stated above, or bake from frozen for 1 1/2 hours (still covered with foil, but remove plastic wrap.) Then uncover and bake for another 45 minutes or so, or until the lasagna is hot and bubbly.
Unbaked: Assemble lasagna (use uncooked regular noodles or no bake noodles).. Cover really well with a layer of plastic wrap and then a double layer of aluminum foil and freeze for up to 2 months. Remove from freezer and allow to thaw in the fridge for 24 hours. Remove plastic wrap. Cover with tinfoil and bake until warmed through and bubbly. about 45 minutes. Remove tinfoil 15 minutes before it's finished baking to allow cheese to get bubbly.
Bottled Red Sauce: If you want to use bottled pasta sauce, instead of making the red sauce from scratch, heat 48 oz pasta sauce in a large skillet. Add cooked and crumbled meat, and chopped basil.