Bring a large pot of salted water to a boil and cook the jumbo pasta shells until just al dente. Grandma said, 'Undercooked shells behave better.' Drain and rinse with cold water, then lay them flat.
Heat olive oil in a skillet and sauté garlic until fragrant. Add spinach and cook until fully wilted. Let it cool, then chop it finely. Grandma insisted: 'Water is the enemy of stuffing.'
In a large bowl, combine ricotta cheese, chopped spinach, mozzarella cheese, Parmesan cheese, egg, Italian seasoning, salt, black pepper, and red pepper flakes. Taste it—Grandma always did—and adjust seasoning.
Spoon the creamy filling into each shell. Don’t overstuff—Grandma said bursting shells were a heartbreak. Arrange them seam-side up in the dish.
Pour remaining marinara sauce over the shells and sprinkle with the rest of the mozzarella and Parmesan.
Cover with foil and bake for 25 minutes, then uncover and bake another 15 minutes until golden and bubbly. Let rest 10 minutes—Grandma said patience makes better food.
Scatter fresh basil or parsley on top and serve warm, preferably with people you love.
