1. Pour sugar into an even layer in a large saucepan.
2. Heat on medium-high heat, whisking the sugar until melted. The sugar will clump up first, but will eventually completely melt. This will take about 10 minutes.
3. Once the sugar has melted, stop whisking. You can allow to cook until the sugar has turned to a little darker amber color to get a deeper caramel flavor, if you like. You may notice a nutty aroma. The change in color will happen quickly, so don’t let it go too long or get too dark or it’ll burn. Remove caramel from the heat.
4. Add butter and whisk until combined. The mixture will bubble up, but keep whisking until all the butter has melted and combined.
5. Slowly pour the heavy cream into the caramel and whisk until incorporated. I find it can help to add just a bit at a time until the caramel starts to thin out, then you can add the rest.
6. Cool for about 10-15 minutes before using. Store leftovers in a jar with a lid. Refrigerate up to 2 weeks.