On water, stew chopped onion, add lean minced meat (if desired), salt, thyme, pepper, grated celery and stir until the meat gets brownish color. Stir and remove from cooker. In another pan (ovenproof dish) on the bottom line up cubes and slices of cauliflower thickness of 3-4 mm, and the gaps between the rings fill with the chopped vegetables. Over the layer of cauliflower, pour the meat and put another layer of cauliflower. In the pan in which the meat was fried, whisk 1 egg and 2 egg whites, add 200ml of yogurt and water to the end, and pour this mixture over vegetables and meat. Moussaka is to be baked in the oven at 300 ° C until on the surface appears brownish crust (if you prepare it just for you, you can make a smaller amount and put only one egg). You can prepare this moussaka with broccoli, roasted peppers and other vegetables.