Pre-heat the oven to 180 °C
Pierce the potatoes all over with a fork or tip of a sharp knife and place on a baking tray and into the oven. Rub with a small amount of oil before putting in the oven for an extra crispy skin
After the potatoes have been cooking for 30 minutes remove the outer leaves of the cauliflower and break the cauliflower and broccoli into florets before washing and draining
Place the florets in a pan of boiling water and boil for approximately 5 mins until tender (drain well and set aside). When testing the cauliflower with a knife it should not fall apart
Melt the butter in a saucepan and add the flour to form a roux, stir continuously for about 2 minutes
Add a little milk at a time, continuously stirring or whisking. Stir out any lumps before adding more milk little by little until all of the milk has been used
Take off the heat and stirring the mustard and the cheese
Add the broccoli and cauliflower in one layer to an oven-proof dish and cover with the sauce and top with the remaining cheese
Place in the oven for the remaining potato cook time
Remove the jacket potatoes from the oven, slice in half and top with a spoonful of cauliflower &broccoli cheese