1/2 cup mayonnaise
1 tablespoon brown mustard
1 tablespoon lime (or lemon) juice
1 tablespoon soy sauce
3/4 cup flour
1/2 cup cornstarch
1/2 teaspoon baking soda
3/4 teaspoon salt
1 cup seltzer water, room temperature
1 pound asparagus stalks (about 30), washed, trimmed and patted dry with paper towels
Vegetable oil for frying
Make dipping sauce: In a small bowl, combine mayonnaise, mustard, lime juice and soy. Set aside.
Make tempura batter: In a large bowl, combine flour, cornstarch, baking soda and salt. Whisk in seltzer and stir until smooth.
Heat about 2" vegetable oil in a deep skillet until a drop of the batter sizzles. Place six pieces of asparagus in the tempura batter, turn to coat and fry in hot oil about two minutes. Remove to paper towel-lined sheet pan. Repeat until all are cooked. (Note: if asparagus is very thick, trim bottoms with a paring knife). Arrange on platter and serve with dipping sauce. Makes about 30.