-
1
Bring a large pot of salted water to a boil.
-
2
Cook the shells for 1 minute less than indicated on the box.
-
3
Drain and let cool.
-
4
Spray a 9- by 13-inch casserole dish with nonstick spray.
-
5
Heat a large high-sided skillet over medium-high heat.
-
6
Add the beef and sausage and cook until browned, while stirring and breaking up with the back of a wooden spoon, 3 to 4 minutes.
-
7
Stir in the carrots and onions and cook until softened, about 4 minutes more.
-
8
Stir in the garlic and red pepper flakes if using, and cook until fragrant, about 1 minute.
-
9
Add the crushed tomatoes and simmer on medium-low, uncovered, for 20 minutes.
-
10
Stir in the basil at the end.
-
11
Rinse the spinach in a colander with cold water.
-
12
With water still clinging to the leaves, add the spinach to a large nonstick skillet over medium heat and toss with tongs until wilted.
-
13
Remove from the heat and let cool.
-
14
Once cool, wrap in paper towels and squeeze out any excess moisture.
-
15
Chop roughly.
-
16
Preheat the oven to 350 degrees F.
-
17
In a large bowl, add the spinach, ricotta, 1/2 cup of the mozzarella, 1/4 cup of the Parmesan and the egg and give it a stir until well combined.
-
18
Spread 3 ladlefuls of sauce on the bottom of the prepared casserole dish.
-
19
Stuff each shell with about 1 heaping tablespoon of spinach and cheese mixture.
-
20
Place the shells in the dish and then cover with more sauce.
-
21
Sprinkle the casserole with the remaining 1/4 cup Parmesan and remaining 1/2 cup mozzarella.
-
22
Cover with foil and bake for 30 minutes.
-
23
Remove the foil and keep baking until the cheese is melted and bubbly, another 5 minutes.
