Place asparagus in a steamer basket over 1 in. of boiling water in a saucepan; cover and steam until crisp-tender, about 4 minutes. Drain on paper towel.
Place crust on an ungreased 12-in. pizza pan; arrange asparagus on top. In a bowl, combine the mayonnaise, cheese and mustard; mix well. In a small bowl, beat egg whites until stiff peaks form. Fold into mayonnaise mixture; spread over asparagus.
Bake at 450° for 12-13 minutes or until golden brown. Cut into wedges; serve warm. Refrigerate leftovers.