Lasagne Incassettata Tartuffato from Truffles by Elisabeth Luard

Ingredients

• 350 g (8 oz) green lasagne (dried)
• 1 tablespoons olive oil
• 1 black summer truffle (about 50 g/2 oz)
• 2 level tablespoons unsalted butter
• 2 level tablespoons plain flour
• 4 tablespoons diced prosciutto
• 600 ml (1¼ pints) full-cream milk
• Salt and pepper
• 4 tablespoons mascarpone (or full-fat cream cheese)
• 4 tablespoons grated Parmesan or Pecorino cheese
• 1 egg, well-whisked
• 1 fresh white truffle (30-50 g/1-2 oz), cleaned