Heat the oven to 180°C or 350°F.
Place a large frying pan on a medium to high heat and add one quarter of the butter. Add the mushrooms and fry until browned then remove from the pan and set aside.
Reduce the heat to medium and add the rest of the butter and minced garlic and sauté for 1-2 minutes, until fragrant.
Add the flour, nutmeg, salt, and pepper. Gradually whisk in the milk, stirring constantly to avoid lumps.
Add the tomatoes, broccoli, thyme and oregano and simmer in the sauce for 5 minutes. Then stir in the gnocchi, cooked mushrooms and basil leaves.
Sprinkle mozzarella, Parmesan and breadcrumbs on top.
Bake in the centre of the oven for 20 minutes until the cheesy topping is brown and bubbling. Optional: Place under the grill / broiler for a few minute to get the cheese topping extra crispy.