Peel medium to large carrots thinly, top and tail, then cut into slices, or thin batons. Simmer in salted water for a few minutes until al dente. Drain, run under the cold tap to halt cooking, then drain again thoroughly.
Put the carrots into a saucepan with the butter, and enough ginger beer to come about halfway up the carrots. Sprinkle over a little caster sugar and season with salt. Bring up to the boil, stirring occasionally, then boil until the ginger beer has more or less all boiled away, leaving the carrots glazed with a sweet, buttery gingery glaze. Taste and add more salt if needed.