Cheese Soufflé

Method

1. Heat the oven to 200C (no fan) and put a baking tray on the middle shelf. Brush the inside of a 300 ml straight-sided ramekin generously with 5 g of softened butter, working the brush in upward strokes from base to rim so the soufflé can climb. Tip in 1 tsp of finely grated Parmesan, turn the dish to coat completely, tap out the excess and chill until needed.
2. Melt 15 g of butter in a small heavy saucepan over medium-low heat. Stir in 15 g of plain flour with a wooden spoon and cook the roux for 1-2 minutes, stirring constantly, until it smells biscuity but has taken no colour.
3. Pour in 120 ml of whole milk a splash at a time, whisking hard after each addition so the sauce stays smooth. Bring to a bare simmer and cook 2-3 minutes, whisking, until it is thick enough to hold the trace of the whisk. Season with 1 pinch of fine sea salt, a good grind of white pepper, a small pinch of grated nutmeg and 0.25 tsp of Dijon mustard.
4. Take the pan off the heat and let it cool for a minute. Separate 1 egg, beat the yolk into the sauce, then add 35 g of grated Gruyère and stir until melted and glossy. The base should be thick, warm and strongly seasoned — it will be diluted by the whites. Reserve the white.