Roll out the pastry to an 1/8-inch thick. Butter and flour a tart pan, and lay the pastry in it. Prick the bottom with a fork. Cut the Cheddar into thin strips and place on the bottom of the tart. Then cook the onion in butter until soft. Preheat the oven to 500F. Beat the eggs with the cream and milk, add the herbs and pepper. Pour some of this mixture over the cheese and add salmon strips and onion. Fill the rest of the tart with the egg and cream mixture. Bake for 5 minutes, lower the heat to 425F and cook for another 25 minutes. Drain the asparagus tips and heat them with some butter. Remove the quiche from the oven and decorate with the asparagus tips.
