Melt butter, sugars and syrup and butter in a small heavy based pan and let simmer for 3 minutes, swirling every now and again.

Add cream and half a teaspoon of fleur de sel salt (not table salt!) and swirl again, give a stir with a wooden spoon and taste – go cautiously so that you don’t burn your tongue – to see if you want more salt before letting it cook for another minute on the stove, then pour into a jug for serving.