Many foods that are used as fillers and frauds because they are cheap are also decent foods in their own right. I have had pollack prepared well and memorably in France, (with potatoes, watercress cream and Avruga; paired with an Hautes Cotes de Nuits) ) but suspect most have had it as "krab." When prepared as an honest dish, it can be wonderful, but most of it is as a fraud. See the picture. Moist, firm, infused with delicate watercress that complemented the already delicate flavors of the pollack.
What are your positive experiences with foods usually used as filler or substitutes that were memorable when used on their own?