Lime Icebox Pie Filling

Whisk together 3/4 cup milk and 1/4 cup cornstarch in a 3-quart heavy saucepan, whisking until cornstarch dissolves.

Whisk in sweetened condensed milk and eggs until blended; whisk in lime juice and, if desired, food coloring. Bring to a boil over medium heat, whisking constantly. (

Mixture will begin to thicken when lime juice is first added, and then become thin again during first few minutes of cooking. It will thicken quickly as it comes to a boil.)

Boil 1 minute, whisking constantly, or until mixture thickens.

Remove mixture from heat, and whisk in butter and lime rind until smooth.

Pour filling into a large bowl, and place bowl in a larger bowl filled with ice. Stir regularly until cold (about 10 minutes).