Cardoon Gratin with Gruyère

Remove the tough outer stalks of the cardoons, pull away the stringy fibres from each stalk with a peeler or paring knife, and cut into 6cm batons. Rub each piece immediately with the cut lemon. Fill a large pot with cold water, squeeze in the remaining lemon juice, add 1 tbsp of the flour, and 2 generous pinches of salt — this blanc keeps the cardoons pale.

Bring the blanc to a boil over high heat, add the cardoon pieces, and blanch for 25-30 minutes until completely tender when pierced with a knife — cardoons must be fully cooked at this stage or they will remain tough in the gratin.

While the cardoons blanch, stud the onion halves with the cloves and place in a small saucepan with the warm milk, cream, and bay leaf. Heat over medium-low until steam rises and small bubbles appear at the edges, then remove from the heat and infuse for 15 minutes.

Drain the cardoons thoroughly in a colander and pat dry with a clean cloth. Preheat the oven to 190°C fan / 210°C conventional.

Melt the 50g butter in a medium saucepan over medium heat until foaming subsides, whisk in the remaining 1 tbsp flour, and cook for 90 seconds, stirring constantly, until the roux smells biscuity and turns a pale straw colour.

Remove the onion, cloves, and bay leaf from the infused milk, then pour the warm milk mixture into the roux in a steady stream, whisking vigorously to prevent lumps. Cook over medium heat, stirring constantly, for 5-6 minutes until the béchamel is thick enough to coat the back of a spoon.

Remove the béchamel from the heat, add the nutmeg, white pepper, and 120g of the Gruyère, and stir until completely melted and smooth. Taste and adjust salt.

Butter the gratin dish generously, arrange the cardoon batons in a single even layer, and pour the cheese béchamel over them, ensuring full coverage.

Scatter the remaining 60g Gruyère and all of the Parmesan evenly over the top, then bake on the middle rack for 25-30 minutes until the top is deeply golden and the sauce is bubbling vigorously at the edges.

Rest the gratin for 5 minutes before serving so the sauce tightens slightly and portions hold their shape.