Rinse the carrots. Put them in a steamer set over a pan of simmering water and steam for 8-10 minutes until just tender. Remove from the heat and set aside.
Meanwhile, put the butter and sugar in large pan. Warm over a medium heat until melted and bubbling. Stir in the Dijon mustard, then tip in the steamed carrots. Stir to coat. Transfer to a warm serving dish and scatter over the parsley to serve.