Chop the
shallots or onion finely and fry in the butter in a small enamel or
non-stick saucepan. Add the wine and simmer for 15 minutes over a very
low heat. Then stir this mixture into the brown sauce and simmer for a
further 10 minutes. Before serving, stir in the mustard and tomato
puree. Serve with roast or fried pork, grilled chicken or veal.