How do you handle students laughing at you?

Today I had a student turn my whole class against me and I'm not sure what to do. He was talking with a friend while I was teaching. I told them "Hey you guys need to be quiet. I've already warned you once. If it happens again, it's gonna be a call home and a write up." and he stood up and started pretending to be all scared to make all his friends laugh. So I said "Okay fine. You think this is a game, you wanna treat this like a joke, fine, you do you, that's a write up." And I went over to my desk and wrote his name on my write up list in my notebook. And the whole class just blew up. "Nooooooo. No wayyyyy. It's the ops it's the ops! Teacher going crazyyyyyy." Whole class. Took me like 10 minutes before I got them to calm down again. What am I supposed to do there? It's not like I can punish all 30 of them and they know that. Another teacher said I should threaten them with extra work if they don't stop. But every single one of them was just not taking me seriously.