Fill a large saucepan two thirds full with salted water. Add the oil and bring to the boil.

Add 1 sheet of lasagne, wait about 2 minutes, then add another sheet. Cook only a few at a time and when tender, after about 6-7 minutes, remove from the boiling water and rinse under cold water. Allow to drain.

Repeat this process until all the lasagne is cooked.

Wash and slice the mushrooms, and slice the chicken breast into thin strips.

Melt half the butter in a small frying pan and fry the mushrooms and the chicken.

In a small saucepan, melt the rest of the butter. Stir in the flour and cook for 1 minute.

Remove the pan from the heat and add the milk gradually to the melted butter and flour mixture, stirring well and returning the pan to the heat between additions, to thicken the sauce.

Beat the sauce well and cook for 3 minutes, until it is thick and smooth.

Pour the sauce into the frying pan with the chicken and the mushrooms. Add half the cheese and mix well to incorporate thoroughly Season to taste.

Lay the sheets of lasagne on a board and divide the chicken mixture equally between them.

Spread the chicken mixture evenly over each lasagne sheet and roll up lengthways, like a swiss roll.

Put the rolls into an ovenproof dish. Sprinkle with the remaining cheese and grill under a preheated moderate grill, until the cheese is bubbly and golden brown.