Preheat oven to 400 degrees. With a sharp knife, cut off and discard the upper third of each garlic head, exposing the cloves. (Leave the skin intact below the cut.)
Set the garlic heads, cut-side up, in a small baking dish or grating dish just large enough to hold them. Pour chicken stock over the garlic, add thyme sprigs and season lightly with salt and pepper.
Cover the dish tightly with heavy-duty aluminum foil and bake for 1 hour, or until each clove is soft to the touch and the skin resembles lightly browned parchment.
Serve the garlic with the cooking juices spooned over and pass goat cheese and bread separately.
To eat, break off a piece of bread and spread with a small amount of cheese, then scoop out the garlic puree from one of the cloves with the tip of a knife and spread on top.