For the onion sauce
Roast the onions with the oil in a hot oven until nicely caramelised.
Transfer the onions into a colander and drain off the excess oil.
Place the onions in a pot with the chicken stock and simmer for 1 hour.
Strain the onions from the stock and reduce by half or until the consistency of a loose glaze. Season to taste.
For the celeriac
Place the celeriac into simmering water and cook for 1 hour or until you can pass a nice through the vegetable.
Warm half the butter in the pan and fry the whole celeriac. You’ll need to baste the celeriac continually.
Add in the thyme and rosemary.
Allow the butter to become quite nutty but not black.
Baste until the colour of the celeriac is beautifully brown.
Remove from the frying pan and rest.
Fry the mushroom briefly in the remaining butter with some thyme.
Season to taste.
Place a wedge of celeriac in a warm bowl.
Arrange a few mushrooms and around the celeriac.
Garish with some ramsons and finish with some onion sauce.