I have always known this sauce as butterscotch sauce, but I suppose that toffee sauce would be an equally good name. It is ideal served over ice cream and sliced banana, and is very popular with children - especially when you boil the sauce for a bit too long, and it turns to toffee when you pour it on the cold ice cream! It is a very sweet sauce, so you may not need too much of it. I have suggested that the quantity in the recipe serves 4 to 8, but really it depends on how much you serve out, and how sweet a tooth you have. It's easy to scale up or down - you just use equal weights of the three ingredients. If you use light brown sugar, you get a lighter-flavoured sauce, with a more predominant butter flavour, which I think is better than the sauce you get with dark brown sugar. Variations - If you like, you can add cinnamon, ginger or vanilla to the mixture. But the taste of the sauce tends to overwhelm additional flavourings, so I no longer bother to experiment.