'n

When you see 'n between two English words, it means and. So the sign here means pie and burger. This way of writing and is most common on signs, or names for things, and I think it tries to express the way that people speak. Often when people say and between two words, you can only hear the n. This is very informal, and is supposed to give a feeling of being friendly, casual, and in no way posh.

Thanks to A Maxwell, for reminding me of this restaurant!