Be sure to impress your guests with these tasty mini asparagus and Gruyère quiches, perfect for picnics and light snacks. Place the butter, flour and salt in the bowl of a food processor and pulse until partly combined. Add 40ml of cold water and pulse again a few times until it forms a dough. Wrap in cling film and chill for 30 minutes. Heat the oven to gas 4, 180°C, fan 160°C. Bring a saucepan of water to the boil and blanch the asparagus for 2 minutes. Lightly beat the eggs in a jug then stir in the double cream, Gruyère and dill. Lightly dust a clean surface with flour and roll out the pastry to 5mm thick. Using an 8cm fluted cutter cut out rounds and line a 12 hole cupcake tray. Divide the asparagus between the pastry rounds keeping the tips to decorate. Pour over the egg mixture and top with the asparagus tips. Bake for 20-25 minutes until risen and golden.