You can of course also use fresh spinach. Just clean and wash it and then briefly steam
Preheat the oven to 180°C. Wash the herbs, pat dry and chop finely. Clean the mushrooms and cut or chop into small cubes. Brown the chopped mushrooms in a hot cocotte with a good splash of olive oil, then remove from the pot and season with the chopped herbs, salt and pepper.
Peel the onion and the garlic cloves and chop finely. Now sauté the onion and half of the garlic in a little olive oil in the cocotte. Stir in the frozen spinach and cook for 15 minutes until the liquid has evaporated. Remove from the heat and let cool.
Season the cooled spinach mixture with the ricotta, the mozzarella chopped into small pieces, and the grated Parmesan cheese, mix well in a bowl and season with salt, freshly ground pepper and nutmeg.
Fry the remaining diced garlic in the cocotte on a medium heat until golden brown and add the tomato passata. Bring to the boil and simmer for 3 minutes. Season with salt and pepper and leave the sauce in the pot.
Lay out the fresh pasta dough sheets lengthwise on a clean work surface. Working quickly to prevent the pasta dough drying out, sprinkle the sheets with water and spread the spinach-ricotta mixture on top. Flatten the mixture slightly and place the diced mushrooms on top. Roll up the sheets to make cannelloni tubes and cut each into 3 pieces. Place the pieces side by side in the tomato sauce. Bake in the cocotte with the lid on in a preheated oven (bottom rail) for 40-45 minutes. Halfway through the cooking time, remove the lid, so that the surface becomes brown and crisp.