It could be, but only if the three foods form a dish that is seen as a single combination normally eaten together. You could say, for example, "My favourite food is egg, bacon and sausage". You could even say "My favourite food is fried egg, bacon, sausage, mushrooms, black pudding, grilled tomato and fried bread". (But it might be simpler to say "My favourite food is a full English breakfast".)Is it OK if I use "is" after food since I have three food names?