The Byzantines have the curious custom (strange to Westerners) of elevating a triangular portion of bread, named the Panagia (All-Holy), in honour of Our Lady, at the end of the main monastic meal. Lifting it up, the priest cries "Great is the Name" and all reply "of the Holy Trinity" and then he cries (while moving the morsel horizontally, so as to complete making the Sign of the Cross with it) "All-Holy Theotokos, save us" (sôson hêmas), to which all reply "Through her intercessions, O God, have mercy and save us".
By its taking up, it is in a manner offered to God and blessed; and with it a blessing is imparted to all the faithful present who glorify the Lifegiving Trinity and invoke the Mother of God, thus implicitly commemorating the Incarnation of the Eternal Word, Who, being One of the Trinity, became Man to save us. It is a blessing to us when we bless God, and bless Him in His Saints, especially in God's Mother.
The Orthodox assert that this act is of apostolic origin - they state that after Our Lord's Ascension, the Apostles wherever they were always set aside some bread as Our Lord's portion at table (till He come again), which they would partake of, leaving a morsel, and had the custom of blessing the Trinity when lifting this last piece up at the end of the meal (recalling Christ's Ascension), ending by saying, "O Lord Jesus Christ, save us". However, soon after Our Lady's Dormition, she appeared to them in heavenly glory at the very moment they were conducting this dinnertime ritual - revealing that she had been resurrected and assumed into heaven - and they were so astonished that they spontaneously exclaimed, "All-Holy Theotokos, save us": and this has been said instead ever since.
The loaf for this purpose (which has been blessed at the Liturgy) is brought into the monastic refectory with some fanfare, and all come eventually to receive of it, perhaps dipping it in the wine provided and waving it over the censer if these be present. The triangular portion kept back until the end of the meal is set aside in a sometimes elaborate vessel on a table - the panagiarion - by itself, oft with a candle and even a censer before it, and there may be icons of the Trinity and the Blessed Virgin with it also. (Occasionally, even a chalice of wine is present - the whole rite is redolent of Eucharistic symbolism.)
This fragment of bread is a reminder that the Virgin Mary was blessed above all women to bring forth her Son Who is the Living Bread come down from heaven to nourish us unto everlasting life of soul and body. The portion is triangular to call to mind the Trinity, One of Whom became incarnate of the Virgin Mary to save us; and it is lifted up to make the Sign of the Cross to recall Christ's saving Passion. It is offered as a blessing of Our Lady, or, more correctly, through her as His Mother it is offered to bless Him Who was born of her. By being lifted up, it is exalted from humble bread to a vehicle of blessing; this also calls to mind Holy Mary's unique glorification in her bodily Assumption into heaven.
(Please consult Aquaro's article on the Lifting of the Panagia for more information.)
Forgive me for even mentioning it, and I cast no aspersions upon this decent and orthodox rite, but there once was a most unusual heretical practice that fraudulently resembled this one - for the sect of the Collyridians, against whom St Epiphanius wrote in his Panarion (late 4th C.), were mad women who idolatrously worshipped the Virgin Mary, and vainly offered unto her small cakes and bread rolls, feigning to act as priests!
In this they emulated, not the true Israel of God, but the disgraceful perversions of those who bowed down before the Moon-goddess or demon: "...the women knead the dough to make cakes to the queen of heaven..." (Jer. vii, 18). Unfortunately there are not lacking crazies to-day who claim this as a wretched warrant for goddess-worship and other heterodox nonsense, deceiving and deceived.