To make the pastry. Place the flour, butter and salt into the bowl of a food processor. Process until the mixture resembles fine breadcrumbs. Add the water a little at a time until a smooth dough is formed. Don't over mix. Wrap the pastry in plastic wrap or foil and refrigerate for 30 minutes.
Roll out the pastry on a floured surface until it is about 3mm thick. Use the rolling pin to support the pastry and transfer it to a 26cm loose based tart tin. Carefully tuck the pastry into the tin then trim any excess. Chill again for another 30 minutes.
Blanch the asparagus and peas in boiling salted water for 1 minute. Drain and refresh in cold water.
Beat the eggs with the cream and milk. Season with salt and pepper then pour into the pastry case.
Scatter over the cheese, then the asparagus, peas and spring onions. Finish with the chopped chives. Place in the oven on the bottom shelf. (Shelf Level 1).
Bake for 15 minutes, then turn down the heat to 170°C and bake for another 30-35 minutes or until set and golden brown.