Peel and finely chop the onion. Peel ginger and chop very finely. Clean and wash the chillies, halve them lengthwise, remove the seeds and chop very finely. Peel, wash and cut sweet potatoes into pieces of about 2 cm.
Cut off the ends of the carrots. Peel the carrots and cut them into slices about 1 cm thick.
Heat the oil in a large pot. Sauté onion, ginger and chili in it for about 2 minutes while stirring. Add sweet potatoes and carrots. Add 1 l hot water. Stir in stock. Bring everything to the boil and simmer for about 20 minutes.
Preheat the oven for the cheese stollen (electric stove: 220 °C/circulating air: 200 °C/gas: see manufacturer). Grate the Gouda. Mix with 2 tablespoons of crème fraîche and egg yolk. Season with salt and pepper. Spread slices of bread with the cheese mixture.
Sprinkle each slice with 1⁄4 TL rosemary. Bake in a hot oven on a grill grid lined with baking paper for 3-5 minutes until golden brown. Remove from the oven.
Puree the soup with a hand blender until creamy. Stir in 2 tablespoons of crème fraîche. Season soup with salt and pepper. Serve with the cheese stollen.