chicken hearts
Small, firm chicken hearts with a robust, faintly iron-like flavour and a pleasantly chewy bite.
Chicken hearts are sold fresh at butchers, markets and Turkish, Eastern European or Latin American grocers, and frozen in some ordinary supermarkets. Before cooking, trim off the fat and the vessel ends at the top.
Substitute:
Chicken gizzards are the closest match but are tougher and need much longer cooking; small cubes of chicken thigh cook just as quickly but taste milder and lack the firm, springy bite.