Score fat and skin on duck breasts. Place duck breast skin side down in a large cold skillet with a heat safe handle. Put skillet on stove and turn burner on to moderate heat. Cook breasts 5 to 8 minutes, turning once the skin crisps and most of the fat is rendered. Place the skillet in the oven and cook another 9 to 12 minutes. Meat should be pink at center.
Arrange greens on individual plates or 1 large platter. Arrange frissee and scallions on bed of baby greens.
Combine shallots, vinegar and marmalade. Let stand 10 minutes. Whisk in extra-virgin olive oil.
Slice duck breast and serve 6 to 8 ounces per person, arranging the sliced duck on the salad. Grilled or sauteed chicken or pork is delicious with this dressing as well. Pour dressing evenly over duck and salad.