Arrange croissants, cut sides together, on a 12- by 15-inch baking sheet. Heat in a 375| oven until croissants are crisp outside and warm inside, about 8 minutes.
Meanwhile, bring about 1 inch water to boiling in a 10- to 12-inch frying pan over high heat. Add asparagus; cook, uncovered, until stems are tender when pierced, 5 to 7 minutes. Drain and serve hot.
Or, if made ahead, immerse in ice water until cold. Drain, cover, and chill up until next day. To reheat, immerse in a large bowl of very hot-to-touch water (about 140|); let stand until warm, about 5 minutes; drain.
Set the bottom half of a croissant, cut side up, on each plate. Cover croissants equally with crab; put 2 or 3 asparagus spears atop crab on each plate. With a slotted spoon, place 1 egg on each croissant half. Pour sauce equally over eggs. Set a croissant top beside each portion.
Hollandaise sauce. In a blender or food processor, whirl 2 large egg yolks, 2 tablespoons lemon juice, and 1/16 teaspoon cayenne to mix. With motor running, slowly pour 3/4 cup (3/8 lb.) hot melted butter or margarine into yolk mixture. Serve; or, if made ahead, pour into small metal bowl, cover, and chill up to 2 days. To reheat, set bowl in a larger bowl; pour hot-to-touch tap water into larger bowl to height of sauce in inner bowl; stir often until sauce is warm, about 5 minutes.
COPYRIGHT 1988 Sunset Publishing Corp.