Cut the tops off the chestnuts and roast them in the oven for 20 minutes.
Remove the outer and inner skins, and put the chestnuts into a stew-pan with half of the butter and enough stock to cover them.
Lay greaseproof paper over the top, put on the lid, and cook gently for 45 minutes or longer, until the chestnuts are quite tender.
The chestnuts should absorb all the stock in the cooking.
When cooked, rub all through a fine wire sieve.
Thoroughly mix this puree with the remaining butter and the milk.
They may not require all the milk, depending on how much stock has been absorbed.
Season with pepper, a very little salt, and a pinch of castor sugar.
Re-warm and use.