Preheat oven to 400. Saute the onions in 2 tablespoons of the butter for 10 minutes, until soft but not browned.
In another pan, heat 4 tablespoons of the butter and saute the crumbs until crisp.
Melt the remaining butter in a small saucepan. Spread one phyllo pastry sheet out on a large board and brush with butter. Put another pastry sheet on top and brush with more butter. Repeat until all sheets have been used.
Spread the onions evenly on top of the pastry, keeping the edges clear.
Put the asparagus over the top of the onions and sprinkle with three-quarters of the crumbs and the parsley.
Fold over 2 inches all around the pastry, then fold the long edges over to make a roll. Place the roll, seam side down, on a baking sheet and bend it around into a horseshoe shape.
Brush with remaining melted butter and sprinkle with the remaining crumbs. Bake 40 minutes or until golden.
Garnish with parsley sprigs, lemon slices and asparagus tips.
Combine yogurt and herb dressing ingredients and serve with strudel.