The brain paste outlined here enhances the lamb in a manner similar to a classic mustard and bread crumb covering – but with greater richness and complexity of flavour.
150 g lamb or veal brains, soaked in cold water for 24 hours and rinsed
2 cloves garlic
1/4 cup parsley leaves
25 g wild garlic mustard greens (or 1 extra clove garlic)
1/4 cup butter, softened
1 tsp Dijon mustard
Kosher salt and freshly ground black pepper
2 lamb racks, Frenched and trimmed down to the eye
Grapeseed or canola oil
Preheat oven to 450°. Bring a large pot of water to the boil, add salt, and return to the boil. Add lamb brains and poach for 2 minutes (5 for veal brains). Shock in ice water. If using calf’s brains peel the web-like exterior membrane and discard (if using lamb brains, there is no need). Remove the stem and visible blood vessels.
Combine garlic, parsley and garlic mustard greens in the bowl of a processor. Pulse until finely minced. Add butter and pulse until combined. Add mustard, brains, and season generously. Pulse briefly, but stop when the mixture is still a little chunky. Add 1 tablespoon of panko and pulse until incorporated. Repeat until mixture becomes sufficiently thickened as to be spreadable.
Line a cookie sheet or baking sheet with plastic wrap. Pour mixture onto the sheet. Spread in a rectangle of the same width as your racks of lamb, and a thickness of about 5 mm (1/4-inch). Cover with plastic wrap and chill until firm – about 1 hour.
Meanwhile, generously season the racks of lamb with salt and pepper. Heat a skillet on medium-high heat, add the oil, and sear the racks on all sides until nicely browned – about 4 minutes per side. Transfer to a baking sheet to cool.
Once the brain mixture is chilled, cut two rectangles from the sheet of approximately the same dimensions as the top side of the eye of the lamb racks. Arrange the racks ribs down in a roasting pan. Drape the brain crust over the meat, and roast until the brain crust is bronzed and the meat is done – about 125 F internal temperature (rare). Set aside to rest for 10 minutes. Then portion and serve.