Clean the mushrooms, cut in half lengthways and then cut into thick slices. Peel and halve the onion and cut into rings. Mix the sour cream with the flour in a bowl.
Heat some oil in a deep pan and fry the mushrooms in it until they have clearly shrunk, this takes about 3 minutes. Then add the onion rings and fry for another 3 minutes. Deglaze with vegetable stock, bring to the boil and simmer gently for about 5 minutes. Season well with salt and pepper.
Reduce the heat and stir in the sour cream. Add parsley, lemon juice and pumpkin seed oil and bring to a boil. Fold the tortellini into the sauce, drizzle with a little pumpkin seed oil and serve.
A mixed salad with yogurt dressing is recommended.