He's doing exactly what Sougo is asking, so Sougo thinks he's being a super good boy. Not in like a dog or child way, but in like... look, you get it.

He laughs softly and smiles as he moves up to try and start picking apart what to do here.

"Thank you, Tamaki-kun. That's very kind of you."

And he means it! He knows how much Tamaki likes his sweets.