As a matter of fact...
1. As a matter of fact, we were just talking about you when you came in.
2. As a matter of fact, I was the one who did it.
3. I finished it yesterday, as a matter of fact.
A: I wish I could unsay the sharp words to him. He must hate me very much.
B: He doesn't mind. As a matter of fact, he's very pleased.
A: Really? Oh, thank Goddness!