Volume 3, Book 44, Number 664:
Narrated Salama (radiallaahu `anhu):
Once the journey food diminished and the people were reduced to poverty. They went to the Prophet (sallallaahu `alayhi wasallam) and asked his permission to slaughter their camels, and he agreed. ‘Umar (radiallaahu `anhu) met them and they told him about it, and he said, “How would you survive after slaughtering your camels?” Then he went to the Prophet (sallallaahu `alayhi wasallam) and said, “O Allah’s Apostle! How would they survive after slaughtering their camels?” Allah’s Apostle (sallallaahu `alayhi wasallam) ordered ‘Umar (radiallaahu `anhu), “Call upon the people to bring what has remained of their food.” A leather sheet was spread and al I the journey food was collected and heaped over it. Allah’s Apostle (sallallaahu `alayhi wasallam) stood up and invoked Allah to bless it, and then directed all the people to come with their utensils, and they started taking from it till all of them got what was sufficient for them. Allah’s Apostle (sallallaahu `alayhi wasallam) then said, “I testify that None has the right to be worshipped but Allah, and I am His Apostle. “
Ask Allah to bless your food before eating it. Say Bismillah and pray for barakah, especially when it’s for a gathering. You’ll see that you won’t run out of it till everyone’s had their fill. Sunnah 101.