Heat a large skillet over medium-high heat. Pour olive oil into hot pan and heat until shimmering. Cook mustard seeds in hot oil until they begin to pop, about 1 minute; immediately add peppercorns and fenugreek seeds.
Gently lay the lamb chops in a single layer into the skillet; add curry sauce and basil and stir. Bring the sauce to a boil, place a tight-fitting lid on the skillet, reduce heat to low, and cook until the lamb is tender, 60 to 70 minutes.
Remove lid from skillet. Continue to cook and stir until most of the liquid has been reduced and the meat has a brownish look on all sides, 10 to 15 minutes more.