Exclusively Christian would be the fact that all people gather in one building (the church) or near the building to have the food blessed.
I think this is also practiced in some sects of Judaism, I could be wrong though.
Muslims also bless food: 'Bhiksha is a devotional offering, usually food, presented at a temple or to a swami or a religious Brahmin who...' although, since Islam is a descendent of Judaism/Christianity that's obviously where it came from.
Also druids used to bless food at public gatherings during Celtic times.
I disagree with you about eggs, eggs were a powerful symbol of fertility, they would most certainly have been 'blessed' by druids during Eostre/Ostara, or they were at least used by druids during the festivities and were used to put spells on women who wished to become pregneant.
The painting of eggs seems to have been happening long before records were even written down.