How to Make It
Steam the parsnips in 1 inch of water, covered, until very tender, 6 to 10 minutes; drain. Transfer to a food processor along with the milk, 2 tablespoons of the butter, ½ teaspoon salt, and ¼ teaspoon pepper; process until smooth.
Heat the remaining 3 tablespoons of butter in a small skillet over medium heat. Add the garlic and coriander and cook, stirring occasionally, until the butter is foamy and beginning to brown, 3 to 5 minutes.
Heat the oil in a large skillet over medium-high heat. Season the lamb with ½ teaspoon salt and ¼ teaspoon pepper and cook, in 2 batches, until an instant-read thermometer inserted into the thickest part (avoiding the bone) registers 130° F, 3 to 5 minutes per side for medium-rare.*
Serve the parsnip puree topped with the lamb and spiced butter. Sprinkle with the herbs.
* This recipe includes the Real Simple test kitchen’s preferred cooking temperatures (considered safe by many experts) for steaks and chops cooked to their juicy best. For maximum food safety, the U.S. Department of Agriculture recommends temperatures of 145° F for all beef, lamb, and pork steaks and chops.