2 pounds asparagus
1 teaspoon kosher salt, plus more to taste
1 teaspoon sugar
1 large egg
1 teaspoon Passover mustard
1 tablespoon red-wine vinegar
Freshly ground pepper to taste
¾ cup vegetable oil
Snap the ends off the asparagus. Then, using a vegetable peeler, peel about 2 inches off the thickest part of the stems.
Bring a big pot of water, with the salt and the sugar, to a boil. Drop in the asparagus, and cook for about 10 minutes, depending on the thickness. Drain, and set aside.
To prepare the hollandaise: Separate the egg, and put the yolk in the bowl of a food processor fitted with a steel blade. Add mustard, red-wine vinegar, and salt and freshly ground pepper to taste. Pulse to combine. With the motor running, gradually drizzle in the oil until it emulsifies and you have a thick, creamy mayonnaise.
Beat the egg white to stiff peaks. Mix half of the beaten egg white into the mayonnaise, then gently fold in the other half to make a very fluffy sauce. Serve the warm or room temperatue asparagus with the hollandaise on the side.