Combine first 5 ingredients in a large bowl, stirring with a whisk until smooth, pour into the top of a double boiler. Cook over simmering water until mixture thickens (about 6 minutes) or until a thermometer registers 160 degrees F., stirring constantly. Remove from heat. Place pan in a large ice-filled bowl for 20 minutes or until mixture comes to room temperature, stirring occasionally.
Spoon 1 tablespoons whipped cream into each of 8 (8-oz.) glasses, top each serving with 1 tablespoons crumbs and 3 tablespoons lime mixture. Repeat layers once, ending with lime mixture. Top each serving with 1 tablespoons whipped cream; sprinkle with lime rind, if desired. Serve immediately.