Cut the courgettes lengthwise using a knife, peeler, or mandoline slicer. Slice the mushrooms.
Chop the onion. Heat the oil in a pan and sauté the onion until soft. Add the Planet of Plants mince and break it up with a spatula.
Sauté the mince for 2-3 minutes, then add the mushrooms, followed by the chopped tomatoes, dried oregano, salt, and pepper. Stir well.
In a bowl, mix the ricotta and the egg. Add a bit of salt.
Take an oven-proof dish and put the first layer of courgettes on the bottom. Add the mixture with the mince, then add 2-3 tablespoons of ricotta and egg on top. Spread the cheese mixture over the mince. Add another layer of courgettes and keep layering until you have used up all the ingredients. Finish with a layer of courgettes coated with the ricotta mixture.
At the end, sprinkle with grated Parmesan and bake in the oven at 180°C for about 45 minutes. The top of the casserole should be golden-yellow when done.
