Slice the truffle thinly. Beat the eggs in a bowl and incorporate most of the slices. If you have some brandy or the liquid from the jar if using preserved truffles, add a teaspoonful to the eggs.
Leave to stand for 30 minutes so that the eggs absorb the truffle’s perfume. Heat the butter in an omelette pan. Season the eggs and pour half the mixture into the pan. Make an omelette as you are accustomed. Once you’ve turned this one out, make another in the same pan. Scatter your remaining truffle slices over the tops and serve forth.