Cook the cauliflower and broccoli in boiling, salted water for 5 minutes. Drain and plunge them at once into cold water to retain colour and prevent further cooking.
Stir a little of the yogurt into the flour to make a smooth paste, then stir in the remaining yogurt. Heat the yogurt mixture slowly, stirring constantly.
Stir in the cottage cheese and half grated cheese, season with salt and pepper and remove from the heat.
Put the mushrooms, cauliflower and broccoli into a greased, shallow baking dish, mix the vegetables to coat them thoroughly.
Stir the butter, oats, bran cereal and nuts together and stir in the remaining cheese. Sprinkle over the dish.
Place in a preheated oven and bake for 45 minutes. Serve hot.