Halve the apricots and remove the pits. Melt the butter and sugar in a pan and add the rosemary and apricots. Season with a pinch of pepper and salt and deglaze with vinegar. Briefly sautee the apricots and remove them from the heat as soon as they begin to lose some juice.
Season the foie gras with salt and pepper and pan-fry on medium heat, 2 minutes each side.
Peel the potatoes and cut in half. Cook in salted water and drain. Let cool a few minutes then mash with a wooden spoon. Slowly add the pieces of cold butter and season with salt and nutmeg. Then add scalded milk, still stirring with the wooden spoon until desired consistency.
Smooth some mashed potatoes onto a warm plate, add the foie gras and apricots. Garnish with a sprig of fresh rosemary.