Jerusalem artichoke, ham and mushroom

INGREDIENTS     500g (1lb 2oz) pack all-butter puff pastry     500g (1lb 2oz) Jerusalem artichokes     2tsp olive oil     1 large leek, finely sliced     200g (7oz) mushrooms, sliced     3 cloves garlic, finely chopped     90g (3¼oz) shredded ham hock     Large handful parsley, roughly chopped     Large sprig of thyme, leaves stripped     85g (3oz) Gruyère cheese, grated     3 eggs, lightly whisked     200ml (7fl oz) milk     250ml (9fl oz) double cream     2tsp English or Dijon mustard METHOD Preheat the oven to 190°C/fan 170°C/gas 5. Roll out the pastry and line a 23cm (9in) tart tin, leaving extra pastry hanging over by 2.5cm (1in). Chill 30 minutes then bake blind, as in the Lemon Tarts on page 71. Peel and slice the artichokes thinly. Boil for 15-20 minutes until tender, then drain. Heat the oil and sauté the leek for a few minutes, push to the side of the pan, add the mushrooms and cook until golden, then add the garlic and cook for 1 minute. Tip into the tart shell, scatter over the ham, herbs, half the cheese, and the artichokes. Mix the eggs, milk, cream, mustard and season. Pour into the tart and scatter in the remaining cheese. Bake 40 minutes until golden. Cool 10 minutes, trim the edges and serve.