Get Ahead: Steam, cover and chill the leeks a day before you want to cook this.
Takes 1 hour 5 minutes
In this recipe, leeks are cooked slowly in cream and cheese until soft and golden. If your oven is running too hot, the cream may split – this doesn’t matter at all in terms of how it tastes, it simply results in a slightly less pretty dish.
1. Cut the leeks into roughly 5cm (2 inch) lengths, then halve lengthways down the middle. Wash well to remove any grit or soil, but try not to let the layers of leek come apart too much.
2. Set a steamer basket over a pan of simmering water. Add the leeks and steam them for 8 minutes. Meanwhile, whisk together the cream, crème fraîche, cayenne, salt, pepper and mustard, making sure the mustard is completely combined into the sauce.
3. Place a pan large enough to take the cream mixture over a medium heat. Add the butter and when melted add the flour. Cook for a minute, stirring to form a paste, then gradually add the milk, until you have a smooth sauce. Remove from the heat and whisk in the cream mixture, beating until absolutely smooth.
4. Preheat the oven to 170°C (335°F), gas mark 3–4 and grease a medium-sized ovenproof dish (ours is 24x18cm/9½x7 inches) with oil. Arrange the leeks in more or less a single layer in it, cut sides facing up. Sprinkle over one-third of the cheese. Pour the cream mixture evenly over the leeks, opening up the layers to ease the cream between them, then sprinkle over the rest of the cheese.
5. Place in the oven and bake for 40 minutes. If the leeks on top seem to be browning too fast, place a sheet of foil over the top of the dish, but don’t cut the cooking time as the leeks need it to become tender.
• 4 big leeks, roots and green parts trimmed away, tough outer leaves removed
• 200ml (7fl oz) double cream
• 2 tablespoons full-fat crème fraîche
• A generous pinch of cayenne pepper
• A pinch of salt • 1 tablespoon Dijon mustard
• A knob of butter
• 1 tablespoon plain flour
• 200ml (7fl oz) milk
• Flavourless oil, for greasing
• 100g (3½oz) Cheddar cheese, finely grated
• Freshly ground black pepper