Peel the carrots, keeping the tops.
Lay them flat in a sauté pan, cover with water, then add the butter and coriander seed. Season with salt and pepper. Cover with a circle of baking parchment, of the same diameter as the inside of the pan, and with a 1 cm diameter hole in the middle.
Cook over a gentle heat until all the water has evaporated. Keep warm.
Wash the oranges, take off the zest and cut into thin julienne strips. Scald them for 2 minutes, cool and dry. Peel those oranges right down to the flesh, and quarter.
Put the sugar and vinegar in a saucepan and heat slowly to produce a dark blonde caramel. Add the chicken stock, orange juice and zest. Season with salt and pepper and cook for 20 minutes over a gentle heat.
Use a knife to score a criss-cross pattern in the skin side of the magrets and season with salt and pepper.
Cook for about 15 minutes and keep warm using a sheet of aluminium foil.
Mix the Grand Marnier and starch together in a small bowl. Pour that preparation into the sauce, stirring all the time. Add the orange quarters and the residual cooking juices from the magrets and simmer for 5 minutes.
Slice the magrets and arrange them on the confit carrots.
Pour the sauce over.
