Bring a saucepan of water to the boil over a high heat. Add the broccoli, cauliflower, sprouts and carrots. Cook for 6 to 8 minutes until just tender. Drain and transfer to an ovenproof baking dish.
Meanwhile, in a saucepan over a medium heat melt the butter then add the cornflour. Remove from the heat and gradually whisk in the milk. Return to the heat and whisk continuously until the sauce thickens. Add in the cheese, reserving a little to sprinkle on top, and stir until melted.
Pour the cheese sauce over the vegetables so that they are just covered. Place the sliced potatoes on top to cover all the vegetables and sauce, then sprinkle more cheese on top.
Bake in the preheated oven for 20 to 30 minutes until the cheese has melted and the potato is tender and golden brown. Remove from the oven and serve hot.
Substitute the Brussels sprouts with sweetcorn, peas, green beans or what ever vegetables you like.