2 tablespoons olive oil
1 pound bulk sage-flavored sausage
1 (10-ounce) fresh chopped spinach
1 (4-ounce) jar diced pimentos, drained
4 cups grated cheddar cheese
1 1/2 cups grated Gruyère cheese
1/4 cup all-purpose flour
2 cups 2% milk
Kosher salt and freshly
Ground black pepper
9 oven-ready lasagna noodles
4 large eggs, whisked
1. Preheat the oven to 350°F. Grease large pan with olive oil.
2. In a medium skillet, heat the oil over medium heat. Add the sausage and cook, breaking it up with a wooden spoon, until browned, 7 to 8 minutes. Remove the sausage with a slotted spoon and transfer to a medium bowl. Stir in the spinach and pimentos and cook for 2 to 3 minutes, until heated through. Add the sausage and bacon to the spinach mixture and toss to combine. Set aside.
4. Grate the the cheddar and Gruyère into a large bowl and mix. Whisk in the flour and cook, whisking, until slightly browned, about 2 minutes. Add the milk and continue whisking until slightly thickened, about 5 minutes. Remove the pan from the heat and add 3 cups of the grated cheeses. Stir until the cheese has melted, 1 to 2 minutes. Season with 1/2 teaspoon salt and 1/4 teaspoon pepper.
5. Spread 3/4 cup of the cheese sauce over the bottom of the prepared pan. Layer 3 noodles over the sauce, one-quarter of the remaining grated cheeses, and one-third (about a heaping 1/2 cup) of the cheese sauce. Repeat the layers two more times, making sure all the top noodles are covered with the sauce.
6. Add 1 teaspoon salt and 1/2 teaspoon pepper to the whisked eggs and pour over the lasagna. Top with the remaining grated cheeses.
7. Bake for 40 to 45 minutes, until the cheese is golden brown and bubbling and the eggs are set. Remove from the oven and let rest for at least 15 minutes before serving.