Craving something sweet? This will hit the spot!
Liberally grease a 10-inch round spring form cake pan with vegetable oil. Line the bottom of the pan with parchment paper. Line the sides of the pan with a parchment paper so that the parchment paper creates a collar that sits 1 to 2-inches above the pan. Liberally grease the parchment paper.
In a deep medium saucepan add sugar, corn syrup, water, and vanilla. Over medium-high heat bring the mixture to a boil (without stirring) and cook until hard crack stage, i.e. until temperature reads 300 degrees F. on a candy thermometer. This should take about 10 minutes. During the cooking process, if there are any sugar crystals on the sides of the pan, brush the sides of the pan with a clean pastry brush dipped in water.
Remove the sugar mixture from the heat. Working quickly, add the baking soda and whisk to incorporate the soda into the sugar mixture, about 5 seconds. Note the mixture will bubble up when you add the baking soda so be very careful not to touch the hot toffee. Immediately pour the hot toffee into the prepared pan. Let cool and set completely before touching. Break into pieces and serve. Store at room temperature in an airtight container.