Snap mine has just ate 30g of milky bar at 7.30 this morning, theobromide in white chocolate is less than milky bar more for dark or cooking, ring your vets asap for advise as chocolate poisoning developes over a period of time, look out for Sickness/nauesea/restlessness/hyperactivity..
..vets
can give an injection to make the dog sick it up, but only within the first 2 hours.
As Josephine says call the vet now for advice. He will probably be OK but it's always best to err on the side of caution our furry friends are too precious.