Carve grooves into the magrets with a knife, to let the marinade penetrate better, and marinate for about 30 minutes.
Fish the meat out, set it in a frying pan over medium heat for 3-4 minutes on each side, until the pan is full of grease. Pour out the grease, deglaze the pan with a little hot water, and put the meat back in, as well as the marinade. Wait a few minutes for the sauce to thicken.
Grill 2 tablespoons sesame seeds in a dry pan over high heat (careful, they burn fast).
Slice the meat in small, artistic amounts, and serve with the sesame seeds and a little of the sauce.
This goes wonderfully with homemade mashed potatoes.
Recipe by Aliette de Bodard at https://www.aliettedebodard.com/recipes/duck-magret/