01 - Line a 9x9-inch pan with parchment paper, or lightly butter a marble slab for shaping.
02 - In a heavy-bottomed saucepan, combine the sugar, heavy cream, whole milk, unsalted butter, and salt. Stir over medium heat until the butter fully melts and the mixture is smooth and well combined.
03 - Bring the mixture to a boil, stirring constantly. Once boiling, reduce the heat and continue cooking without stirring until the mixture reaches 240°F (soft ball stage) on a candy thermometer.
04 - Remove the saucepan from heat. Add the vanilla extract without stirring it in. Set the mixture aside to cool undisturbed until it reaches 110°F, approximately 30 to 40 minutes.
05 - Once cooled to 110°F, beat the mixture vigorously with a wooden spoon until it thickens, turns creamy, and loses its glossy sheen, about 8 to 10 minutes.
06 - Quickly pour or spoon the thickened candy onto the prepared pan or slab. Gently shape into logs or squares. Allow to set for 20 to 30 minutes at room temperature.
07 - Cut the set candy into approximately 24 pieces. Store in an airtight container at room temperature.