How can you teach a dog to chew food rather than just swallow?

Got a big dog here (golden retriever, age 4 i think) who doesn’t seem to believe in chewing his meals. He just inhales and asks for more. I suspect he gets only a small chance to savor the meal before it’s gone down his throat.

I remember the dog I had growing up who would chew a piece of chicken despite his excitement. This dog here, however, just gulp and gone! It’s slightly disturbing to observe. Right now, I swear he has a whole chicken leg in his stomach unchewed.