Wash the potatoes thoroughly, drain and turn them in a bowl with olive oil. Place potatoes on a baking tray lined with baking paper and sprinkle with coarse sea salt. Bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 1 1/4 hours
Wash the apple, quarter it and cut out the core. Dice apple finely. Mix sour cream, frozen herbs, apples and horseradish. Season to taste with salt, pepper and sugar
Cut the black pudding into slices about 1 cm thick and dice. Peel onions and cut into fine rings. Mix flour and paprika and turn the onions in it. Tap off excess flour. Heat 6 tablespoons of oil in a large pan and fry the onions in it in 2-3 portions until golden brown. Drain on kitchen paper
Clean the pan and heat up again with 2 tablespoons of oil. Put black pudding into the very hot pan and fry it briefly while turning it. Take the baked potatoes out of the oven, cut them crosswise and press them on. Fill the potatoes with sour cream and black pudding. Finally spread onion rings on top. Garnish with lamb's lettuce if desired and serve immediately