Spinach and Gruyere Souffle

Preheat the oven to 200°C (180°C fan). Butter a 1.5-litre souffle dish generously, then dust the interior with the grated Parmesan, rotating to coat evenly. Refrigerate the dish while you prepare the base.

Place the spinach in a large dry pan over high heat and toss until wilted, about 2 minutes. Transfer to a colander, press firmly with the back of a spoon, then wrap in a clean tea towel and wring out as much liquid as possible. Finely chop the spinach and set aside.

Melt the butter in a medium heavy-based saucepan over medium heat. Add the flour and stir constantly with a wooden spoon for 2 minutes until the roux turns pale golden and smells nutty.

Remove the pan from the heat and pour in the warm milk in one go, whisking vigorously to prevent lumps. Return to medium heat and whisk continuously for 3–4 minutes until the bechamel is very thick and pulls away from the sides of the pan.

Remove from the heat. Beat in the egg yolks one at a time, incorporating each fully before adding the next. Stir in the Dijon mustard, nutmeg, salt, pepper, 90g of the Gruyere, and all of the chopped spinach. Set aside to cool slightly.

In a large, scrupulously clean bowl, whisk the 5 egg whites with the cream of tartar on medium speed until they hold firm, glossy peaks — they should not look dry or grainy.

Fold a large spoonful of the egg whites into the spinach base to lighten it, stirring without restraint.

Add the remaining whites in two additions, folding gently with a large rubber spatula using broad strokes from the bottom up, stopping while a few white streaks remain.

Pour the mixture into the prepared souffle dish — it should come to within 2cm of the rim. Scatter the remaining 30g of Gruyere over the surface. Run your thumb around the inner rim to create a shallow channel, which encourages a top-hat rise.

Place the dish on a baking sheet and bake on the bottom third of the oven for 28–32 minutes until the souffle has risen well above the rim, is deep golden brown on top, and wobbles only slightly in the very centre when the oven shelf is gently nudged. Serve immediately.