Have everything right at hand within reach.
Start to melt butter over low to medium heat. Just before butter is melted, add all dark brown sugar at once and stir with wooden spoon until sugar is uniformly wet.
Heat stirring occasionally till it becomes less grainy. Looking like liquids instead of wet sand. 3-5 minutes cooking time.
Then add all the cream at once. Lower heat a little and whisk cream into mixture. When liquid is uniform, turn heat back to medium and whisk often for a total of 10 minutes.
After it has cooked 10 minutes let it rest and cool till it reaches room temperature
When butterscotch liquid is room temperature, take a small taste. Whisk in half the salt and vanilla extract Add more salt and vanilla extract until it taste like butterscotch.
Store in refrigerator for a month.
