Here's a great appetizer for springtime entertaining. The bold, toasty sesame oil adds depth to the classic garlic-lemon sauce. Arrange the crisp-tender asparagus spears, tips up, in a tall, clear glass, with the sesame sauce nearby, served in a radicchio leaf cup to add color. The asparagus can be cooked up to 1 day in advance. The sauce will keep for up to 1 week in a covered container in the refrigerator. Bring both to room temperature for serving.