'flavour the food' would imply that you were going to add flavour (e.g. vanilla) to the food.

'flavour food' on its own is meaningless.

I think what you want to say is 'the flavour of the food was delightful'.

Poo flavour.

No, the word flavour (UK spelling) / flavor (US spelling) is not an adverb.

The word flavour / flavor is a noun (there is a lot of flavour in this dish) and a verb (I will flavour the chicken before cooking).

You taste a flavour and you smell a fragrance

The flavour is chocolate toffee flavour and is wholegrain + is recommended to fill your mouth with a delicious flavour.