1.Pre heat your oven to 200, Then get a pan of salted boiling water and cook the cauliflower & leek for 5 min then drain and leave aside.
2.Now melt the butter in another pan, when it starts bubbling Add the flour and mix it all together, then slowly add the milk while continuously stirring until it’s smooth then add the cream,mustard powder & season with pepper.
3.Now add the cauliflower & leeks to an oven proof dish and cover with the cheese sauce & thyme and put aside n the oven for 25/30 min. Enjoy