Fennel and walnut tart

December This is one of the most delicious winter tarts you'll ever eat. Every mouthful has a different taste. The unusual treacly flavour of roasted bulb fennel is perfect with the rich cheese and the flaky pastry, and the crunch of walnuts adds all-important texture. Vegetarian or not, I'd be happy to eat this as a change for Christmas. A drizzle of truffle oil - diluted in a mild olive oil - makes a good last-minute addition. This is wonderful served with many of the usual Christmas vegetables - Brussels sprouts, cumin carrots and hasselback potatoes.

Unbalanced

% Daily Values based on a 2,000 calorie diet

Step 1

Rub the butter into the seasoned flour, or pulse in a food processor until the mixture resembles breadcrumbs. Add just enough of the egg mixture to bring the pastry together into a ball. Roll out and fill a 28cm flan tin (with a little extra pastry left hanging over the side to allow for shrinkage) and chill for 30 minutes.

Step 2

Preheat the oven to 180°C/gas mark 4.

Step 3

Prick the bottom of the tart with a fork, cover with a round of greaseproof paper or foil and weigh this down with some baking beans or rice. Bake the pastry case blind in the preheated oven for about 15 minutes. Keep the oven on afterwards, ready for roasting the fennel heads.

Step 4

Blanch the fennel heads in boiling water for 2 minutes and then roast them on a baking tray in the preheated oven with a little olive oil, salt and pepper for about half an hour, until they are beginning to turn brown and caramelised at the edges, but still have a bite. Keep the oven on for cooking the tart.

Step 5

Heat the milk in a small saucepan until warm. Melt the butter in another small saucepan and stir in the flour to make a fairly stiff roux. Gradually whisk in the warm milk. Cover and put to one side to cool a little. Then, mix the egg yolks with the yoghurt and Dijon mustard in a separate bowl, and add the mixture to the roux, along with the lemon zest. Season with salt and freshly ground black pepper.

Step 6

Sprinkle the pastry with the grated Parmesan (this acts like flour in the base and absorbs any moisture from the fennel bulbs) and lay the roasted fennel over the tart base, Break the Gorgonzola over the top and toss in the walnuts.

Step 7

Whisk the egg whites until stiff and lightly fold into the roux. Spoon this over the fennel, cheese and walnuts and bake the tart in the oven for about 30 minutes or until risen, golden and set to the touch.