- 250g/9oz shortcrust pastry
- 50g/1¾oz unsalted butter
- 50g/1¾oz plain flour, plus extra for dusting
- 300ml/10fl oz whole milk
- 1 tbsp Dijon mustard
- 1 tsp fresh thyme, leaves only
- 3 free-range eggs, separated, plus 1 egg white
- pinch cayenne pepper
- 150g/5½oz Stinking Bishop, or other strongly flavoured cheese, chopped
- 75g/2½oz unsalted butter
- 300g/10½oz wild mushrooms, cleaned
- 1 garlic clove, chopped
- 1 banana shallot, chopped
- 75g/2½oz toasted walnuts, crushed
- black or white truffle, shaved
- Preheat the oven to 190C/170C Fan/Gas 5.
- Lightly dust a work surface with flour. Roll out the pastry to line a 23cm/9in tart tin. Prick the base of the pastry with a fork but do not trim it. Cover the pastry with baking paper, fill with baking beans and bake 'blind' for 15–20 minutes. Carefully remove the paper and beans and return the pastry case to the oven for 5–10 minutes. Leave to cool on a baking tray. Trim the pastry.
- Meanwhile, melt the butter in a large saucepan. Stir in the flour and cook for 2–3 minutes. Add the milk gradually, whisking all the time, until you have a smooth mixture. Stir in the mustard, thyme, egg yolks, cayenne and half the cheese. Scatter the rest of the cheese into the pastry case.
- In a large, clean, glass bowl, beat the egg whites using an electric hand whisk until soft peaks form. Fold in the custard. Pour into the pastry case. Bake for 20–25 minutes.
- For the wild mushrooms, melt the butter in a frying pan. Add the mushrooms, garlic and shallots and cook for 2–3 minutes.
- To serve, transfer the tart to a serving plate or board. Top with the mushrooms, toasted walnuts and truffle shavings.