Trim the asparagus stalks so that the spears are 5 inches long. In a deep skillet bring 1 1/2 inches salted water to a boil and cook the asparagus until they are crisp-tender, about 2 minutes. In a colander drain the asparagus and rinse under cold water. Drain the asparagus well on paper towels.
In a bowl mash the Boursin with a fork until it is smooth. Cut 1 slice of prosciutto lengthwise into 1-inch strips and spread each strip with about 1/2 teaspoon Boursin. Spread about 1/4 teaspoon mustard over the Boursin and wrap each strip in a spiral around an asparagus spear, trimming any excess. Make more hors d'oeuvres with the remaining prosciutto, Boursin, mustard, and asparagus spears in the same manner.
