In a medium sauce pan over medium-high heat dissolve sugar stirring occasionally with a wooden spoon or rubber spatula (until the sugar begins to get hot then you want to stir constantly.) Cook until sugar turns a deep amber. ( can easily burn so watch closely!) Stir in butter until melted. Carefully add a small amount of heavy cream stirring constantly. It will bubble up. Continue to add cream until all incorporated. Whisk until smooth. Remove from heat and cool. Once it's cool you can pour into a mason jar and store in the fridge. It will thicken as it cools. If you want to sure it warm just pop it in the microwave for a few seconds.