Os à Moelle — Roasted Bone Marrow

Roasted bone marrow (os à moelle) is the rôtisseur's simplest and most decadent preparation — cross-cut or split beef marrow bones roasted until the marrow is soft, trembling, and translucent, served in the bone with coarse salt, toast, and parsley salad. Marrow is almost pure fat (approximately 80%), but it is a specific fat — rich in oleic acid (the same monounsaturated fat that makes olive oil healthy), with a clean, buttery, almost umami flavour that is distinct from any other animal fat. The preparation: have the butcher cut femur bones into 7-8cm sections (canoe-cut lengthwise for presentation, or cross-cut rounds). Soak in cold salted water for 12-24 hours, changing the water 2-3 times — this draws out blood from the marrow, producing a clean white colour. Drain and pat dry. Stand the bones upright on a parchment-lined sheet pan (this prevents the marrow from melting out of the bottom). Roast at 220°C for 15-20 minutes — the marrow should be soft and beginning to pull away from the bone slightly (it jiggles when tapped), but not melted into a liquid. If the marrow is overcooked, it liquefies completely and runs out of the bone — there is nothing to spread on toast. Serve immediately in the bone, with a long, narrow marrow spoon for extraction. The accompaniment: thickly sliced sourdough toast, fleur de sel, cracked black pepper, and a salad of flat-leaf parsley, shallot, and capers dressed in lemon juice and olive oil. The parsley salad's green freshness against the marrow's unctuous richness is a contrast of extraordinary satisfaction. Scoop the marrow onto hot toast, sprinkle with salt, top with a pinch of parsley salad.