Preheat the oven to 230°C/450°F/gas mark 8. Melt the butter in a small casserole, add the carrots and fry for 3-5 minutes, until lightly golden. Stir in the sugar and cook until lightly caramelised. Transfer to the oven and cook for 10 minutes. Pour on the stock and scatter over the coriander seeds, then return to the oven and cook for 8-10 minutes, until the stock has evaporated and the carrots have taken on a beautiful shiny glaze. Add the lime juice and zest and some seasoning, toss together and serve.