Use this recipe when making our Turtle Cake.
Butter sides and bottoms of five 3-inch-high cake pans: 4, 6, 8, 10, and 12 inches square. Line bottom and 2 opposite sides of each pan with parchment paper, covering entire height. Set aside.
Place sugar, the water, and corn syrup in a heavy-bottom 8-quart pot, and stir with a wooden spoon until combined. Place pot over medium-high heat, and cook without stirring until sugar reaches 375 degrees on a candy thermometer. The sugar will turn amber and just begin to smoke. While cooking sugar, use a wet pastry brush to remove any crystals that form on the sides of the pan.
Remove from heat, and slowly add the cream. (The mixture will bubble up, so add cream carefully.) Whisk in butter and salt until fully incorporated. Transfer to a heat-proof glass measuring cup.
Place cake pans on sheet pan. Pour sauce into prepared pans. Refrigerate until firm, about 1 hour. Store in pans until ready to use. To remove squares from pans, lift exposed parchment from pan. Invert onto clean surface, and peel away paper.
The glaze is chilled in pans to make molded squares that are firm enough to handle.