Cut a gash on flat side of chestnuts and put in very hot oven or under broiler flame for 5 to 6 minutes.
Take from oven and remove shells and skins with sharp knife.
Cook chestnuts until tender in boiling milk with celery.
Reserve liquid and discard celery.
Rub chestnuts through fine sieve or put into electric blender.
Season with salt and pepper.
Beat in butter and a little of the strained milk used for cooking chestnuts.