Bring a large pot of salted water to a boil. Cook the giant pasta shells according to package instructions until just al dente. Drain and rinse with cold water. Set aside.
Heat olive oil in a pan. Add chopped onion. Cook over medium heat until golden brown (around 8-10mins).
Add chopped fresh spinach. Cook for around 5 mins, until spinach is wilted. Set aside.
In a food processor or high-speed blender, add the soaked cashews and water. Blend until mostly smooth.
Add the tofu, nutritional yeast, lemon juice, garlic paste, salt and pepper. Blend until smooth, scraping down the sides as needed. Add a splash of water if it’s too thick. The texture should be thick but creamy—like ricotta.
Fold in the onion and spinach mixture. Taste and adjust seasoning if needed (more salt, lemon, or garlic paste, depending on your preference).
Preheat oven to 200℃.
Spread a layer of marinara sauce/ passata on the bottom of baking dish.
Using a spoon or piping bag, fill each cooked shell with a generous amount of ricotta filling. Arrange them in the baking dish, open side up.
Spoon the remaining marinara sauce over the shells. Add grated vegan cheese.
Cover the dish with foil and bake for 25–30 minutes, until hot and bubbly. For a slightly crisped top, remove foil for the last 5–10 minutes of baking.
Let cool for a few minutes before serving.
