Melt butter, sugars and syrup 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.Now you’ve got your sauce, you’re ready to take your next steps: eating it. My suggestions are as follows: In the first instance, and for ease, just dribble it over vanilla ice cream. But next up, please consider adding a warm brownie (regular, not the bacon ones) to this pairing. Or drizzle over chocolate melting-bellied fondant puddings or chocolate cake. Or pour over clotted cream and Christmas pudding. But it is not just this realm that welcomes the sauce: it makes a divine and rakishly chic accompaniment to apple crumble, apple cake or simple baked apple.