Peel and wash the potatoes and cut thinly across without cutting the potatoes. Season the potatoes with salt and place them in an ovenproof dish. Melt butter. Pour over the potatoes, sprinkle with breadcrumbs and bake in a preheated oven (electric range: 175 °C/ gas: level 2) for about 40 minutes.
Meanwhile wash the maties, dab dry and cut into large pieces. Peel onions and cut into rings. Clean and wash radishes and cut them into slices. Drain gherkins and cut into coarse slices.
Stir sour cream and yoghurt until smooth. Season to taste with salt and pepper. Wash the dill, dab dry and pluck. Put something aside for garnishing, chop the rest and add to the sauce. Mix the maties, onions, radishes and gherkins with the sauce.
Arrange potatoes and matie on plates and garnish with dill.