Tip: Butter your soufflé dishes well to help those tiny bubbles of hot air trapped in the beaten egg whites to zoom up the sides and over the top, and you'll soon be heading for the heights.

1. Heat the oven to 190C and butter a 19-centimetre / one-litre straight-sided soufflé dish.

2. Melt 60 grams of butter in a small pan over medium heat, add the flour, and stir constantly with a wooden spoon for two minutes over moderate heat. Add the hot milk gradually, stirring constantly, and cook for three minutes.

3. Add the mustard, grated cheddar, all but one tablespoon of the remaining parmesan (or gruyere) and the sea salt and pepper, beating until smooth.

4. Cool for five minutes, then beat in the egg yolks, one at a time. In a large bowl, beat the egg whites until they form firm peaks. Fold one third of the meringue through the mixture, then gently fold in remaining meringue.

5. Fill the soufflé dish almost to the top and scatter with the remaining one tablespoon of grated parmesan. Run your thumb around the rim to create a tiny groove that will help it rise, place on the centre rack of the oven and bake for 30 minutes or until puffy and golden.

6. Scatter with thyme and serve immediately.

Also try Jill's chocolate and almond souffles for a sweet take on simple souffles.