Visualize the food as blissful wisdom nectar inside a vast jewelled vessel, and offer this to a small Buddha visualized at your heart chakra. Recite, "OM AH HUM" three times to consecrate the food and then offer it with any of the following verses:
Guru is Buddha, Guru is Dharma,
Guru is Sangha also.
Guru is the originator of all (goodness and happiness).
To all Gurus, I make this offering.
You, whose body was formed by a million perfect virtues,
Whose speech fulfils the hopes of all beings,
Whose mind perceives all that is to be known,
To the prince of the Shakyas I make this offering.
The supreme teacher, the precious Buddha,
The supreme practice, the holy precious Dharma,
The supreme guide, the precious Sangha,
To all of the objects of refuge, I make this offering.
As you eat, imagine that Guru Shakyamuni Buddha at your heart experiences bliss from the nectar that you have offered to him. He radiates light which fills your entire body.
Dedicate the positive potential (merit) created by offering the food:
May we and those around us, in all future lives,
Never be separated from the Three Jewels,
Continuously make offerings to the Three Jewels,
And receive the inspiration of the Three Jewels.
When you dedicate, especially remember the sentient beings who created negative karma by harming others and who suffered and died in the process of growing and preparing the food.