Peel and finely chop the onion. Clean and wash the broccoli and divide into small florets. Peel, wash and cut carrots into small cubes. Heat the fat in a pot. Fry the vegetables for about 5 minutes, turning them over.
Deglaze with stock, bring to the boil. Cover and simmer for about 8 minutes. Meanwhile cook the noodles in plenty of boiling salted water for about 8 minutes until al dente. Then drain. Drain the vegetables.
Pour the vegetable stock back into the pot. Stir sour cream and starch until smooth. Stir into the vegetable stock and bring to the boil again. Add the vegetables to the sauce and heat up. Season to taste with salt and pepper.
Roast nut flakes in a pan without fat until golden brown. Arrange noodles and vegetable sauce on a plate. Sprinkle with the hazelnut flakes and serve.