You do not have to say anything. Just give him an exceedingly cold blank look then continue the conversation as if he had said nothing.
To quote the rhyme He only does it to annoy because he knows it teases. If you do not respond and just freeze him then ignore it there will be no point in him saying it.
DD has told me that, as a child, she would think often twice about cheeking me because she knew it would result in the cold stare.
Angela Rayner cleared by HMRC. What a coincidence!

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