Use this recipe to make Martha's Famous Croquembouche. Make one batch at a time (rather than doubling the recipe) so that the caramel stays liquid.
Prepare an ice-water bath. Bring all ingredients to a boil in a small saucepan over medium heat, washing down sides of pan often with a wet pastry brush to prevent crystals from forming. Cook, without stirring, until sugar dissolves, 5 to 6 minutes. Raise heat to high, and cook, swirling pan to color evenly, until syrup is amber, about 5 minutes. Remove caramel from heat, and set bottom of pan in ice-water bath for a few seconds to stop the cooking. Use immediately.