Bone the saddle of lamb completely, trim the fillets neatly, and slice into small, thin cutlets for even cooking.
In a sauté pan, combine the crème de cassis and cranberries. Cook over low heat for 10 minutes to develop deep flavors.
Heat one knob of butter in a separate pan and sear the lamb cutlets for 2 minutes on each side until golden. Keep warm while resting.
Discard the cooking fat, deglaze the pan with cognac, and reduce. Add the cranberry-cassis mixture and ½ glass of water. Reduce further for a rich sauce.
Arrange the warm lamb cutlets on plates or a serving platter. Finish the sauce by whisking in the remaining butter for silky texture, then coat the lamb generously.
Expert Tip: For simplicity, ask your butcher to prepare rib of lamb fillets.
Joëlle's Insight: This recipe, crafted by my husband for American palates, shines with the tart harmony of cranberries and blackcurrant. In season, add fresh blackcurrant berries at the end for extra vibrancy.
