Risotto requires long stirring and constant attention. Chefs, however, use a make-ahead method: Reserve 1 cup of broth mixture; prepare the risotto with remaining broth mixture. Remove risotto from heat; cool and spread in an even layer on a jelly roll pan, cover, and refrigerate for up to 2 days. Just before serving, bring the reserved broth mixture to a simmer in a large saucepan; stir in the partially cooked risotto. Cook until the liquid is nearly absorbed, stirring constantly. Add the sherry during the last 2 minutes, then serve.