Preheat oven to 180C/350F. Grease four ramekins or 6 small ramekins very well (see notes for size).

Bring kettle to boil with plenty of water.

Melt half the butter (i.e. 2 tbsp) in a medium saucepan over medium heat, add the leek and cook for a couple of minutes until softened, then remove from pan into a bowl.

In the same pan, melt the remaining butter, add the flour and stir for a couple of minutes. Then whisking constantly, add 1/4 of the milk, and when it has combined (it will be a thick paste consistency) add the remaining milk, whisking constantly over the medium heat.

Continue to whisk and in a minute or two, it will start to thicken. Once it becomes the consistency of a thick pouring cream, remove from heat, add the cheese and leeks and mix to combine. The cheese does not need to melt. Set aside for 5 minutes to cool slightly, then add the egg yolks, salt and pepper and mix to combine.

Meanwhile, beat the egg whites until stiff then fold a spoonful of the whites into the cheese mixture to lighten it. Then pour the cheese mixture into the bowl with the egg whites and gently fold it to combine. Do NOT over mix as it will knock out the air out of the egg whites, it is mixed enough when there are still slight streaks of white and yellow.

Spoon the mixture into ramekins and smooth the tops. Place in a baking dish then pour boiling water around the ramekins so that it comes half way up their sides.

Bake in oven for about 20 minutes or until puffed up and golden on top. Remove from oven and leave in ramekins for a couple of minutes. Then run a small knife around the edge before turning out the souffles. They will deflate a little as they cool.

To freeze: Once completely cool, cover in cling wrap and freeze. To make, defrost completely (do not use microwave), I usually do this by leaving them in the fridge overnight.

Preheat the oven to 180C/350F.

Place a soufflé on a gratin or pie dish (I used a tart dish), pour 1/4 of the cream over the top, scatter 1 tbsp grated cheese and a pinch of salt and pepper.

Bake for 15 minutes until puffed up and the cream is bubbly and golden.

Serve immediately.