For the herb satchet:
For the soup:
f4 tbsp butter, unsalted
2 garlic cloves, finely chopped
1 onion, diced (brown or yellow)
1/2 leek (white part only), diced into ½” cubes (~ 3/4 cup)
3 celery stems, diced into ½” cubes (~1 1/2 cups)
1.6 lb (peeled weight) celeriac, cut into ⅘” cubes (~2lb unpeeled)
1 large potato, peeled, cut into 4/5″ cubes
6 cups water or stock if you prefer
1 1/2 tsp salt
1/4 tsp pepper
1 cup cream
Bundle the bay leaf, thyme, black peppercorns, and coriander seeds loosely in a small piece of cheesecloth to create a sachet. Tie with cooking twine to secure.
Melt butter in large pot over medium-low heat. Add onion, leek, celery and garlic. Cook for 10 minutes until onion is soft but not golden. Don’t rush this part – this creates an important flavour base so we can make this soup using water not stock.
Add celeriac and potato. Cook for 10 minutes, stirring regularly, until the outside of the celeriac and potato starts to soften. Be careful to not colour the celeriac – we’re going for a white soup here!
Simmer 25 minutes: Add salt, pepper, spice and herb sachet, and water. Bring to a boil, then turn down to a simmer. Simmer for 25 minutes (no lid) until celeriac is very soft.
Add cream, simmer for another 3 minutes.
Remove sachet, then blitz until fully smooth using your method of choice. Stick blender (~ 3 mins), or cool slightly and do it in a blender in batches (Note 5)
Adjust salt and pepper to taste.
Ladle into bowls. Sprinkle with croutons and chives, drizzle with olive oil if desired. Serve with crusty bread for dunking!