Wash artichokes by plunging up and down in cold water.
Cut off stem ends, and trim about 1 inch from top of each artichoke.
Remove any loose bottom leaves.
With scissors, trim away about a fourth of each outer leaf.
Rub top of artichoke and cut edges of leaves with a lemon wedge to prevent discoloration.
Place artichokes in 2 Dutch ovens, cover artichokes with water.
Squeeze juice from lemon wedges into water.
Discard wedges.
Cover artichokes, and bring water to a boil, reduce heat to low, and cook 45 minutes.
Place artichokes upside down on a rack to drain, let cool.
Spread center leaves apart, scrape out the fuzzy thistle center (choke) with a spoon.
Chill artichokes, if desired.
Combine egg yolks and remaining ingredients except butter in top of a double boiler, beat with a wire whisk until blended.
Add one tablespoon butter.
Bring water to a boil. (Water in bottom of double boiler should not touch pan.)
Reduce heat to low; cook, stirring constantly, until butter melts.
Continue adding butter, 1 tablespoon at a time, stirring constantly, until sauce is smooth and thickened.
Remove from heat.
Pour sauce into a serving bowl, let cool slightly.
Serve as a dip with artichokes.