Method

1. Place the bacon, butter and celeriac in a heavy-based saucepan over a low heat.

2. Slice the leek in half lengthways, keeping it together by the root end. Slice in half again, keeping it together at the root end.

3. Starting at the green end, chop the leek all the way along into thin shreds, discarding the root afterward. 

4. Wash the chopped leek well and add to the pan, along with the thyme, mace, salt and freshly ground pepper. Stir well to coat evenly, cover and cook over medium heat for 6 minutes, stirring now and then.

5. Toast the bread on both sides and reserve, keeping warm.

6. Meanwhile, in a bowl, mix together the Caerphilly, ale, mustard, cayenne and season with salt and freshly ground pepper (more pepper than salt). Spread the Caerphilly mixture evenly over the toasted bread and grill for 4 minutes.

7. Meanwhile, increase the heat of the leek mixture and pour in the fish stock and cream. Bring to the boil and simmer for 2 minutes. Stir in the crabmeat and parsley. 

8 Take off the heat immediately and adjust the seasoning if necessary. Add a splash of water or cream if it is not the consistency of a stew.

9. Once the rarebit is golden brown on top, slice each serving in half and serve it at once with the bacon, leek and crab cawl.