Cut asparagus in halves. Discard the woody parts. Cut spears into 1-inch pieces. Cook in salted boiling water until tender, about 6 minutes. Melt butter in a skillet. Add asparagus, scallions, salt and pepper to taste. Cook over low heat for 5 minutes. Puree mixture in a blender. Put through a strainer. Heat in a saucepan with the cream, and keep warm until needed.