Tuna and Mushroom Lasagne

1. Sauté mushrooms in butter, add flour, stir over heat for 1 minute.
2. Add milk gradually, removing from heat when sauce bubbles.
3. Stir in tuna, seasoning and juice.
4. Spoon some sauce into greased ovenproof dish, then place on top a sheet of lasagne which has been dipped in hot water.
5. Continue to layer sauce and lasagne, ending with sauce.
6. Sprinkle with cheese and bake in a pre-heated oven at 180°C/350°F/Gas 4 for 20-25 minutes.