Heat the margarine, fry the spring onions until soft.
Add stock and bring to the boil, simmer for 5 minutes.
Add watercress, boil for 15 seconds, then remove from heat.
Season. Cool, then blend.
To assemble pithiviers:
Pre-heat oven to Gas Mark 4/ 180C/350F.
Place the ready rolled pastry, folded on a lightly floured board and cut out 4 rounds with a 13cm/ 5inch plain cutter.
Place the pastry rounds on a greased baking sheet, brush with soya milk and sprinkle with sesame seeds.
Place in the oven for 15 minutes until well-risen and golden brown.
Set aside and keep warm.
Filling:
Roast the garlic in the oven for about 10 minutes, then remove them from their skins.
Set aside.
Steam the asparagus and the sweetcorn.
Set aside.
In a saucepan heat the margarine, sprinkle with the flour and cook the roux for 2 minutes stirring continually.
Remove from the heat and add the soya milk.
Continue stirring.
Place back on the heat and continue to stir until the sauce thickens.
Stir in the wine, cook for a 2 minutes, then remove from the heat.
Mix together the pine nuts, mustard and roasted garlic and add to the sauce, beating constantly.
Add the parsley and the vegetables.
Cut the pastry cases horizontally in half and remove the pastry inside.
Spoon the vegetable mixture into the pastry base and top with the pastry lids.
Serve the pithivier on an individual serving plate with the heated watercress sauce.
