cooked all the way through
When you cook thick food like American-style steak or pork chops, sometimes the outside of it gets cooked while the middle is still raw. When this happens, you say that it's "not cooked all the way through". When something is cooked all the way through, that means it's done on the outsides and in the middle.
Another way to say this is "completely cooked" or "cooked in the middle".