This is traditional Chinese food in Shandong province，We usually eat this in Tomb Sweeping Day。
Tomb Sweeping Day (清明节, Qīngmíng jié) is a one-day Chinese holiday that has been celebrated in China for centuries. The day is meant to commemorate and pay respect to a person’s ancestors. Thus, on Tomb Sweeping Day, families visit and clean the gravesite of their ancestors to show their respect.
In addition to visiting cemeteries, people also go for walks in the countryside, plant willows, and fly kites. Those who cannot travel back to their ancestors’ gravesites may opt to pay their respects at martyrs parks to pay homage to revolutionary martyrs.

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