Peel, halve, and poach the pears in 300 ml (½ pint) of water, the lemon juice and sugar. Save half of the peel.
Sauté the shallots in one tablespoon of the oil until golden. Deglaze with the Madeira, add the stock and half the pear peelings and simmer for 8 minutes. Strain into a clean saucepan and add half of the sorrel. Season the venison. Heat the remaining oil in a heavy frying pan