Multi factor poisons exist. You can't die from any single component, but combine them and then you die.
You can safely consume the food, because its only 1 factor. The silverware, and the wine suggested by others would be excellent targets for the 2nd and/or 3rd factor.
Obviously having 3 factors introduces some chance of failure, but you can use them more liberally as no single ingredient will cause death.
I would suggest something far more devious. This requires knowledge of the kings habits, but his personal chief would know these. First add as much salt as you can without destroying the taste of the food. Even add small amount of salt to the wine if you can. Server as many foods as possible to make him thirst all the time.
Fact: The human body can only handle about 5 gallons of fluid. At least 2 of those are your own blood.
Have a drinking contest with the King and his buddies. Get the King drinking and keep him drinking. The more drunk he is the more you can get him to drink. He will drown himself to death internally, and the salt will help force the body to retain the water,wine, or etc.
Have a potato in your pocket to absorb the salt out of your wine. Additional, try to spill more without being totally obvious about it.
After everyone is drunk into a stupor(or passed out on the floor), and then you can just give the posion to him in his wine.