Cheese Souffle

Preheat the oven to 200°C (fan 180°C or 400°F). Generously butter a 1.5-litre souffle dish, then coat the interior evenly with 20g of the grated Gruyere, tipping out any excess. Chill the prepared dish in the refrigerator.

Separate the eggs, placing the 5 whites into a large, scrupulously clean bowl and the 4 yolks into a small bowl. Measure out all remaining ingredients.

Melt the 30g butter in a medium heavy-based saucepan over medium heat until foaming subsides. Add the flour and whisk constantly for 2 minutes until the roux turns a pale biscuit colour and smells nutty.

Remove the pan from the heat and pour in the milk in a steady stream, whisking vigorously to prevent lumps. Return to medium heat and whisk continuously for 3–4 minutes until the bechamel is thick enough to coat the back of a spoon and pulls away slightly from the sides.

Remove from the heat and stir in the mustard, cayenne, nutmeg, salt and pepper. Beat in the egg yolks one at a time until fully incorporated, then stir in the remaining 100g of Gruyere and all of the Parmesan until melted and smooth. Transfer to a large wide bowl and press a sheet of cling film directly onto the surface.

Allow the bechamel base to cool to room temperature, about 15 minutes, before continuing.

Add the cream of tartar to the egg whites and beat with a stand or hand mixer on medium speed until foamy, then increase to high and beat until the whites hold stiff, glossy peaks — they should not look dry or clump in the bowl.

Stir one-third of the egg whites vigorously into the bechamel base to lighten it.

Add half of the remaining whites and fold gently with a large rubber spatula, cutting down through the centre and sweeping around the base in broad strokes, until just combined with a few white streaks remaining.

Add the final third of whites and fold again until no white streaks remain — work quickly and do not over-mix.

Pour the mixture into the prepared souffle dish; it should come to within 2cm of the rim. Run your thumb around the inner rim of the dish to create a shallow channel, which encourages an even rise.

Place the dish on a baking sheet on the centre rack of the preheated oven and bake for 28–32 minutes until the souffle has risen 4–5cm above the rim, the top is deep golden brown, and the dish wobbles only slightly in the centre when gently nudged — serve immediately.