Had one's cake, say

ATE

What you might do after blowing out birthday candles.

This clue plays on the phrase "have your cake and eat it too," which means wanting two conflicting things at once. Here, "had one's cake" hints at the action of eating it, so the answer is simply "ATE." The "say" part signals that "cake" is just an example—you could also "have" ice cream or pie, but the key is the act of consuming it. It’s a clever way to turn a common idiom into a straightforward verb.