Rinse the carrots and 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.
To serve, transfer to a warm serving dish and scatter over the parsley.