Bone marrow butter leftover sourdough croutons

Preheat your oven to 200°C (180°C fan)

Place the marrow bones on a roasting tray and roast 15–20 minutes, or until the marrow inside becomes soft and begins to pull away from the bone

Remove from the oven and let cool slightly

Use a small spoon or a knife to carefully scoop out the soft marrow from the bones. Discard the bones and set the marrow aside

In a bowl, mix together the extracted bone marrow and unsalted butter until smooth and well-combined

Stir in minced garlic, fresh thyme and a pinch of salt and black pepper

Toss the bread with the bone marrow butter mixture until evenly coated

Spread the bread in a single layer on a baking sheet

Bake for 10–15 minutes, or until the croutons are golden and crispy, tossing halfway through to ensure even browning

Meanwhile, prepare the celeriac soup. Heat the olive oil in a large pot over a medium heat

Add the chopped onion and garlic, and cook for about 10 minutes or until the onion has softened

Add the diced celeriac and Jerusalem artichokes, and cook for another 5 minutes, stirring occasionally

Pour in the vegetable stock, bring the mixture to a boil, then reduce the heat to a simmer

Cook for 30 minutes, or until the vegetables are tender and easily pierced with a fork

Use a stick blender to blend the soup until smooth and creamy. Alternatively, blend in batches using a jug blender, making sure that steam can escape the blender safely

Stir in the cream (if using) and season with salt and black pepper to taste

Ladle the soup into bowls and top with a generous handful of crispy bone marrow butter croutons

Garnish with fresh parsley and a drizzle of olive oil, if desired