Pre-heat the oven to 180’C
Heat a frying pan to a low-medium temperature and gently fry the onion and the leeks with the butter until soft.
While your veg is cooking, make your béchamel by heating the 70g of butter and the cornflour in a saucepan, stirring to make a smooth paste.
Add a good splash of milk and whisk until in has combined with the paste and is no longer lumpy.
Add the remaining milk and continue to stir until the mixture has thickened.
Once you have a consistency that coats the back of your spoon, turn off the heat and stir in the cream cheese and half of the grated cheese – continuing to stir until melted.
Add the mustard, ham and the leek mixture and stir into the pasta.
Tip the mixture into an oven-proof dish and top with the remaining cheese.
Give it a good twist of pepper before baking in the oven for 40 minutes until lovely and crisp
Serve with salad and garlic bread and enjoy!