What is Plant with thistle-like flower heart is cooked?

The plant you're referring to is likely artichoke, specifically the globe artichoke (Cynara cardunculus var. scolymus). Its edible buds contain a thistle-like flower heart, which is prized for its tender, flavorful flesh. Artichokes are often steamed or boiled and served with dips, making them a popular delicacy in various cuisines.