Preheat and prepare your dish. Heat the oven to 375°F (190°C). Lightly oil a 9x13-inch baking dish and spread a thin layer of marinara on the bottom to prevent sticking.

Cook the shells (if needed). If your manicotti aren’t no-boil, cook them in salted water until just shy of al dente. Drain and lay them on a lightly oiled sheet pan so they don’t stick or tear.

Sauté the spinach. In a skillet, warm olive oil over medium heat. Add garlic and cook 30 seconds until fragrant. Add spinach and a pinch of salt. Cook until wilted (fresh) or heated through (frozen). Transfer to a colander and press out excess moisture. Chop finely.

Make the filling. In a bowl, combine ricotta, 1 cup mozzarella, Parmesan, chopped spinach, egg, basil or parsley, a pinch of nutmeg, salt, and pepper. Mix until creamy and well combined. Taste and adjust seasoning.

Fill the shells the easy way. Spoon the filling into a large zip-top bag or piping bag and snip a wide corner. Gently pipe the filling into each manicotti shell. If a shell tears, tuck it in between others; it will bake up fine.

Assemble. Arrange the filled shells in the baking dish. Ladle marinara over the top, making sure each shell is well coated but not drowning. Sprinkle with the remaining mozzarella and a little extra Parmesan.

Bake. Cover the dish loosely with foil (tent it so the cheese doesn’t stick) and bake for 20 minutes. Remove foil and bake another 10–15 minutes until the sauce bubbles and the cheese is melted and lightly golden.

Rest and serve. Let it rest for 5–10 minutes before serving so the filling sets. Scatter fresh herbs on top and finish with a few grinds of black pepper or a pinch of red pepper flakes.