It’s not typically polite to be chewing your food and talking at the same time. People don’t like it when you eat your food with your mouth open.
Well, two of my favorite things in the world are eating, and talking. I like to be efficient, and my time is valuable. So if one can kill two birds with one stone, then why not go for it?
All you really need to do is put the napkin in front of your face as you’re talking. That’s the trick. As long as nobody has a side view of your mouth, as long as food doesn’t fall out, and as long as your words are audible, then yes, you can talk and eat at the same time.