A "foreign" ingredient slipped in here - puy lentils, which are easy to find in most good supermarkets. If you can't find puy, use green lentils instead.
1. Gently cook the lentils with a bay leaf in the water until they are soft. Drain and cool.
2. Roast small beetroot (leave the skins on) in a medium oven until tender. When the beetroot have cooled, slip off the skins and chop the beetroot into small dice.
3. Sear the duck breasts in a very hot pan until both sides are cooked through. Rest in a warm oven for 15 minutes.