Heat 1 tablespoon of olive oil in a large skillet over medium heat. Add chopped onions and minced garlic, sautéing until translucent, about 3-4 minutes.

Stir in 5 cups of fresh spinach, cooking until just wilted, roughly 2-3 minutes. Remove from heat and mix with 15 ounces of ricotta, ½ cup of grated Parmesan, and 1 beaten egg until combined.

Fill a large pot with salted water and bring to a gentle boil. Carefully add 12 manicotti tubes and cook for about 6-7 minutes until al dente.

Drain the pasta, rinse under cold water, and set aside to cool.

Using a piping bag or spoon, gently fill each manicotti tube with the creamy spinach filling. Arrange on a plate.

Preheat your oven to 350°F (175°C). Spread a thin layer of marinara sauce in a 9x13 inch baking dish.

Arrange the filled manicotti in a single layer, drizzle with more marinara sauce, and sprinkle mozzarella cheese on top.

Cover with foil and bake for 30 minutes. Remove foil and bake for an additional 10 minutes until golden brown.

Let it rest for 5 minutes before serving. Garnish with fresh herbs and drizzle with olive oil.