I’ve tried lots of recipes and methods, and found this to be the best, easiest, least fussy, and it’s ready in 15 minutes. You’ll never want store bought again! Before you even start, make sure you have everything in front of you that you will need, including the glass jar and oven mitts. You’re working with boiling sugar and your full attention on the recipe is necessary.
In a large saucepan add the sugar, water, and corn syrup. Bring to a boil over high heat, whisking until sugar has dissolved.
Allow the mixture to boil for 7 to 12 minutes, or as necessary, for it to turn caramel-colored. Keep a watchful eye on the color to prevent burning. The final stage where the mixture turns from pale amber to that perfect shade of caramel can go quickly, in less than 30 seconds. Throughout the boiling time, you can swirl the pan gently every couple minutes, but the less the sugary mixture gets on the sides of the pan, the better in preventing crystallization in the final sauce.
As SOON as the sauce has turned caramel-colored, reduce the heat to low. Carefully and slowly pour in the heavy cream. It will bubble up, so give it a quick whisk. Add in the vanilla and salt, if using, to taste. Whisk until sauce is smooth and combined, and let it boil another 1 minute, which helps thicken it up.
Transfer sauce to a measuring cup then transfer to a glass jar or heat-safe container. Allow sauce to cool uncovered to room temperature; sauce thickens considerably as it cools. The caramel will keep airtight at room temp for at least 1 month.