Prosphora: The Altar Breads 

The next in the series of videos about aspects of the Divine Liturgy the faithful rarely witness, produced by St. Volodymyr Cathedral of Toronto and St. John the Baptist Ukrainian Orthodox Church in Oshawa, Ontario.
In this film, Fr. Bohdan Hladio demonstrates the preparation of Prosphora: the leavened Altar Breads that are offered at the Orthodox Divine Liturgy. Fr. Bohdan explains the symbolism behind the two layers which comprise each loaf (reflecting the dual nature of Christ - both God and man) and the meaning of the seals with which the prosphora are stamped prior to baking. He describes the differences in Ukrainian and Greek/Byzantine traditions of prosphora preparation. In Ukrainian custom, five smaller loaves are used, recalling the five loaves in Scripture at Jesus' feeding of the multitude. These often bear distinctive seals denoting their use at the Liturgy of Preparation (the Proskomedia):
• three prosphora bear a seal composed of a cross flanked by the letters IC XC NI KA ("Jesus Christ Conquers") - one of these will become the Lamb, sacrificed at Communion; one will be used for commemoration of the living; the other for the commemoration of the dead;
• one loaf bears a seal indicating that the loaf is to be used in commemoration of the Mother of God (the seal is often a stylized rendering of the name "Марія" (Maria), an icon of the Theotokos, or a large triangle with embellishments reflecting the triangular dimensions of the particle to be excised and placed on the diskos in the Virgin's honour - the largest, apart from the Lamb itself);
• the remaining prosphoron often bears a seal with nine smaller triangles, each one of which is cut from this loaf in commemoration of the nine ranks of Saints.
In Greek churches, it is common to use one prosphoron, much larger in dimensions than those commonly used in Slavic churches. The Byzantine seal is consequently not only necessarily larger, but also incorporates all of the seals (for the Lamb, the commemoration of the Theotokos, the Nine Ranks of Saints, the living and the dead) that would commonly be used into one. In Greek communities, it is still tradition for family members to bring offerings of bread they have baked themselves or purchased to the Liturgy. Particles from these loaves are placed upon the diskos at the Proskomedia in commemoration of living and the departed family members of those who present the offering. In Ukrainian and some Slav churches, it is much more common for those charged with baking the prosphora to also prepare smaller loaves for this purpose. In both cases, these loaves are returned to the family after Liturgy to be taken home and consumed, often a little at a time, until the offering might be made again.
Fr. Bohdan briefly touches on the divergent tradition of using unleavened bread in the Armenian, Roman Catholic (and subsequently, Protestant) Churches, a practice attested to in the latter half of the 6th century in the case of the Armenian rite; but only becoming common in the Western Church in the 11th century.
Finally, he offers advice for those who feel called to prepare prosphora for their own parishes: consult with and obtain the blessing of your priest; use items dedicated solely to the purpose of prosphora-baking as much as you are able; approach the task with a clean and untroubled conscience, with compunction and in a spirit of prayer:
Lord, Jesus Christ, Son of God, have mercy on me, a sinner.
Господи, Ісусе Христе, Сину Божий, помилуй мене, грішного (грішну).
Κύριε Ιησού Χριστέ, Υιέ Θεού, ελέησόν με τον αμαρτωλόν.