Marinate the lamb cutlets — to a large non-metallic bowl, add the lamb cutlets, olive oil, half the sprigs of fresh rosemary, dried oregano, lemon juice only, 3 smashed garlic cloves, sea salt, and freshly ground black pepper. Toss to fully coat, cover the bowl, and refrigerate for a minimum of 20 minutes but longer if you like.
Make the white bean purée — transfer the drained butter beans, 2 garlic cloves, sea salt, onion powder, and extra virgin olive oil to a blender or small food processor, and blend until you have a fairly smooth consistency. Taste, season with a little salt if you like, and blend again, then transfer to a bowl and refrigerate until ready to use.
Cook the lamb cutlets — heat a griddle pan over medium-high heat and use tongs to transfer the lamb cutlets to the pan, cooking them for 2 minutes each side for medium-rare, 3 minutes each side for medium, or longer if you like. When they’re done, transfer them to a tray, cover with foil, and let them rest for 5 minutes.
Plate and serve — spread the white bean purée over a large serving plate, use tongs to arrange the lamb cutlets on top, along with the flowering rosemary sprigs and lemon slices. Serve with warm flatbreads, leftover white bean purée, and more lemon wedges. A Greek salad and tzatziki also make great sides.