1. Put the meat in a pressure cooker. Add the bay leaves and peppercorns and cover with water. Cook under pressure for 20 minutes for every 500g plus an extra 20 minutes. This means 1kg tongue will cook for an hour. If you use two smaller tongues, calculate the cooking time by using the weight of the larger of the two tongues.
2. Remove the meat carefully from the cooker and set aside to cool for 15 minutes. Carefully peel the skin off the meat – use a paring knife if it won’t come off. Let the meat cool completely, slice thinly and keep in the fridge until needed.
3. Sauce In a glass bowl, mix the mustard powder, sugar, eggs, salt and vinegar. Put the bowl on top of a small pot filled with boiling water or a double boiler and whisk until the mixture becomes thick and creamy (about the consistency of pouring cream).