Put water on to boil; preheat the oven to low. Peel the potatoes and the celeriac, cut into small chunks and put into separate saucepans. Cover both with boiling water, add salt and cook gently for 15 minutes, or until soft.
Meanwhile, heat the oil over moderate heat and fry the sausages for 10 minutes, turning frequently to brown well, then transfer to the oven to keep warm.
Drain the celeriac and purée with the milk in a blender, or by hand. Drain the potatoes, add the butter and mash by hand. Combine the celeriac and potato purées, then crumble in the Stilton cheese; season with salt, pepper and mace, and mash again.
Pile the purée into a warm dish and arrange the sausages around the mash or on top of it. Serve with a selection of hot and mild mustards, and chutneys and pickles.
NUTRIENTS PER SERVING:
good source of vitamins A, B group, C, E and folate.