Step 1

Preheat the oven to 375 degrees. Cook pasta until al dente according to package directions.

Step 2

Heat oil in a large skillet. Add onion and cook until tender about 3-4 minutes. Add in garlic and cook for an additional minute.

Step 3

Add the spinach and cook until wilted, about 2 minutes.

Step 4

Transfer the spinach mixture to a large bowl and add in ricotta, mozzarella, Parmesan, egg, salt and pepper. Stir to combine.

Step 5

Spread about 1/2 of the sauce in the bottom of a 8 x8 or 9 x 9 baking dish.

Step 6

Stuff shells with the spinach cheese mixture and place in the baking dish.

Step 7

Top with the remaining sauce and bake for 20-30 minutes or until warmed through.

Step 8

Serve immediately with basil and parmesan cheese, if desired.