German-Style Potato Soup with Vienna Sausages

Peel the potatoes, carrots, celeriac, and onion. Cut the potatoes and celeriac into cubes of about 2 cm, dice the carrots and onion more finely, and slice the leek into thin rings.

In a large pot, melt the butter over medium heat. Add the onion and leek and sauté for 3–4 minutes, until softened but not browned.

Add the carrots, celeriac, and potatoes, stir, and heat through for 2 minutes. Pour in the vegetable stock, add the bay leaf and marjoram, and season with salt and pepper.

Bring the soup to a boil, then reduce the heat and simmer, covered, for 25–30 minutes, until the potatoes and root vegetables are tender.

Remove the bay leaf. Set aside about a quarter of the vegetables, then partially mash the rest of the soup with a potato masher or blend briefly with an immersion blender, leaving some chunky texture. Return the reserved vegetables to the pot.

Slice the Vienna sausages into rounds. Add them to the hot soup and warm through for 3–5 minutes without letting it boil hard, so the sausages don't turn tough.

Taste the soup and adjust with salt and black pepper if needed. Serve hot, sprinkled with finely chopped parsley.