Over medium to medium-high heat, bring your mixture to a boil. Watching carefully that it doesn’t boil up and over.
Let the mixture boil on medium to medium-high heat until it reaches 260ºF. This could take 9-12 minutes. From 220ºF to 260ºF it can feel like forever. If it’s been 10 minutes and the temperature isn’t rising steadily, you’ll need to up the flame little by little until you start to see it rise.