Preheat the oven to 200°C/fan oven 180°C/gas mark 6. Roll out the pastry on a lightly floured surface, sprinkle with the poppy seeds, then press them into the pastry with the rolling pin. Use to line a 20 x 30cm (8 x 12 inch) oblong tart tin. Line with foil or nonstick baking paper and baking beans and bake ‘blind’ (i.e. without a filling) for 15 minutes.
Take the flan from the oven and remove the foil or paper and baking beans. Reduce the oven temperature to 180°C/fan oven 160°C/gas mark 4.
Lightly cook the asparagus in boiling water for 2-3 minutes. Run cold water over it, then drain well.
Tear the peppers into strips and arrange them in the pastry case with the asparagus and Stilton. Beat together the eggs and crème fraîche. Season with black pepper. Pour into the flan case, then bake for 30-35 minutes, until set. Serve warm or cold, garnished with basil.
Cook’s tip: Try not to handle the pastry too much – it should be kept as cool as possible to give a light, crisp finish. Make mini versions in bun trays to serve as canapés or snacks.