Halakha Kejadian 27:28: Kitzur Shulchan Arukh & Shulchan Arukh, Orach Chayim

Before reciting the berachah, place both hands on the bread because the ten fingers are symbolic of the ten mitzvos involved in making bread. [The ten are] 1. It is forbidden to plow with a team comprised of an ox and a donkey. 2. It is forbidden to plant diverse species together. 3. The stalks that fall during harvesting must be left for the poor. 4. A sheaf forgotten in the field must be left for the poor. 5. A corner of the field must be left unharvested for the poor. 6. It is forbidden to muzzle a working animal. 7. A portion of grain must be separated and given to the kohein (priestly family). 8. A tenth of the remaining harvest must be given to the Levite. 9. A tenth of the remaining harvest is then separated to be taken up to Jerusalem and eaten by the owner. 10. A piece of the dough is separated and given to the kohein. For this same reason there are ten words in the berachah of Hamotzi, and ten words in the verse (Psalms 145:15): "The eyes of all look expectantly to You" etc., and ten words in the verse (Deuteronomy 8:8): "A land of wheat and barley" etc., and ten words in the verse (Genesis 27:28): "And may Hashem give you" etc. When you pronounce the Name of Hashem, lift up the bread. On Shabbos lift up both loaves, and recite the berachah with concentration, making sure to enunciate clearly the letter hei in the word Hamotzi. Also allow a short pause between saying the word lechem and the word min, so as not to slur over the letter mem. After reciting the berachah, you must immediately eat the bread, because it is forbidden to interrupt between saying the berachah and eating [the bread], even to answer Amein. You should try to eat a kazayis of bread without interruption.

Put both hands on the bread when you are about to bless "Hamotzi"; for the 10 fingers are reflective of the 10 mitzvot that are dependent on bread. Additionally, there are 10 words in the blessing of "Hamotzi" and 10 words in the following verses: Psalms 104:14, "He causes the grass to grow for the cattle, and grass for the service of man: that he may bring forth bread out of the land." Psalms 145:15, "The eyes of all look to you expectantly, and you give them their food at the proper time." Deuteronomy 8:8, "A land of wheat and barley, of vines, figs, and pomegranates, a land of olive trees and honey." Bresheit 27:28, "May G!d give you from the dew of heaven and fat of the earth, and an abundance of grain and wine."