Put the corn in a sieve and let it drain. Peel, wash and roughly grate the potatoes. Peel onions. Grate 1 onion finely, dice coarsely. Mix potatoes, grated onion, corn, flour and egg.
Season with salt and pepper. Line 2 baking trays with baking paper and brush lightly with oil. Form 6 buffers per tray from 2-3 tablespoons of mixture. Bake one after the other in a preheated oven (electric cooker: 225 °C/ convection oven: 200 °C/ gas: level 4) for about 25 minutes.
In the meantime thaw the peas. Clean the spinach, wash thoroughly and drain in a colander. Peel garlic and chop finely. Heat the butter in a wide saucepan. Sauté garlic and diced onion in it.
Add spinach in portions and steam for about 3 minutes. Add broth and peas and cook for about 4 minutes. Season to taste with salt, pepper and nutmeg. Wash the chives, dab dry and cut into small rolls.
Mix yoghurt, oil and chives. Season to taste with salt, pepper and sugar. Arrange buffer on spinach-peas-vegetables. Add chives and yoghurt.