Can my dog eat that!?

My dog ate an entire chocolate cake and he was cool but he ate one piece of chicken and we had to take him to the vet :(

Is he allergic to the chicken or was something wrong with the chicken? And how big is your dog?

Big dog that can eat tons of chocolate but only really small amounts of protein

That's probably your dog. But most big dogs need their protein. And the reason they can eat so much chocolate is because of their proportionate size to the point where chocolate becomes potent enough to affect them. Think about it like this with chocolate: it takes less venom from a snake to kill a child than an adult