Chop chicken into small pieces until almost cooked.
Chop broccoli into small pieces and boil until almost cooked.
Melt butter into a large saucepan, fry onion gently for 5 minutes. Add flour and cook for a further 2 minutes.
Remove pan from heat, add stock & milk gradually stirring continuously. Return pan to the boil, still stirring, simmer until sauce thickens
Remove Sauce from heat, add chicken broccoli, sweetcorn, herbs, salt & pepper. stir thoroughly.
In a medium-large oven proof dish, layer sauce & lasagne sheets, aiming to get a minimum of 3 lasagne layers. Finish with a layer of sauce, sprinkle with cheese & bake for 35 mins 200 degrees c/ gas mark 6.