Peel the onion and garlic and dice both finely. Heat the oil and butter in a saucepan and fry the cubes.
Peel the potatoes, carrots and apple. Cut out the core of the apple and roughly grate everything. Add the rasps to the onion cubes in the saucepan and stir-fry.
Pour the stock, bring to the boil, close the lid and remove the heat. With the residual heat, everything becomes wonderfully soft. Finally, season with salt and pepper.
Brown the butter. Put the soup in preheated plates, drizzle with a little brown butter and garnish with a little parsley.
Of course, other vegetables such as kohlrabi, radish, zucchini and leeks cut into fine rings can also be used. Vegetable, poultry or beef broth are suitable as broth.