Pre heat the oven at 220 'c for 10 minutes.Place one sheet of pastry on prepared tray.. lightly brush it with water and top with another sheet. Using a small knife, make a 2cm border around edge of pastry.
Meanwhile, mix ricotta cheese and basil pesto together in a small bowl. Season with salt.
Spread ricotta mixture over the puff pastry and arrange asparagus, in a single layer.Season with pepper. Scatter in the chopped walnuts.Bake for 20 to 25 minutes until the pastry is golden. Serve hot with pesto.