Gently cook the leeks in the butter
and olive oil until soft but not coloured.
Add the celeriac and stock, bring to the
boil and simmer until the celeriac is soft.
Add the bags of watercress and blend
until smooth, then season. Cool. Will
freeze for up to 3 months.
To serve, defrost the soup in the fridge
overnight, then tip into a saucepan
and reheat. Top each toasted baguette
slice with some goat’s cheese, then
add a slice to each bowl with a sprig