People in which country celebrate their Halloween by eating candy skulls?

Mexico.

In Mexico, the Day of the Dead (Día de Muertos) is a three-day holiday that celebrates the lives of deceased loved ones. During this time, people visit the graves of their loved ones and decorate them with flowers, candles, and food. They also eat traditional foods such as pan de muerto (bread of the dead) and drink atole (a hot corn drink). One of the most iconic symbols of the Day of the Dead is the sugar skull (calavera de azúcar). These skulls are made of sugar, water, and egg whites, and they are often decorated with colorful icing and beads. They are given as gifts to loved ones and friends, and they are also used to decorate altars and graves.