In a frying pan, cook bacon over medium heat until crisp. Remove with a slotted spoon to plate lined with kitchen paper; drain, reserving 1 tablespoon dripping. In the dripping, saute onion until soft; drain.
Cut six asparagus spears into 10cm-long spears for garnish. Cut remaining asparagus into 2.5cm pieces. In a saucepan, cook all of the asparagus in a small amount of boiling water until tender; drain.
In a bowl, toss the bacon, onion, asparagus pieces, cheese, flour, salt and pepper. Pour into pastry case. In a bowl, beat eggs and cream; pour over bacon mixture. Top with reserved asparagus spears. Bake at 200 C / Gas mark 6 for 30 to 35 minutes or until a knife inserted near the centre comes out clean and pastry is golden brown. Let stand for 10 minutes before cutting.
To cut fat and calories, I sometimes use half milk, half cream instead of the full 125ml of cream. Also, this quiche is great with different cheeses, like Cheddar or Emmental.