01 -
Set your oven to 375°F and cook the pasta shells just until tender by following the instructions on the package.
02 -
Add oil to a big pan and heat it up. Sauté the onion until soft (about 3-4 minutes), then toss in the garlic and cook for another minute.
03 -
Add the spinach into the pan and let it cook down until it's just wilted, which only takes around 2 minutes.
04 -
In a big mixing bowl, combine the cooked spinach mixture with ricotta, mozzarella, Parmesan, egg, salt, and pepper.
05 -
Cover the bottom of an 8x8 or 9x9 dish with half a layer of marinara sauce.
06 -
Fill up each shell with the spinach-cheese mix and organize them neatly in the baking dish.
07 -
Pour the rest of the marinara on top and bake for 20-30 minutes, or until everything is hot and bubbly.
08 -
Sprinkle more Parmesan and some chopped basil over the top before serving it nice and warm.