Heat oven to 180°C
Heat oil in large saucepan. Cook onion, add mince, break up lumps and brown. Add carrot, zucchini and sauce. Add pepper & salt to taste. Cook for 15-20 min.
In another large saucepan melt butter. Add flour and stir for 1 minute. Gradually add milk, stirring until sauce just starts to thicken. Turn off heat.
In a large dish or foil tray, place about 1 cup meat sauce. The lasagne is now made up of 4 fairly even layers - lasagne sheets, meat sauce, white sauce then cheese.
Cook for about 30 minutes or until golden. Let sit for 1/2 and hour before serving.
If freezing, cook for about 20 minutes, cool, then place in a large zip lock bag with paper towel on the top. Thaw, then reheat .