To make Jamie Oliver Potato Dauphinoise, preheat the oven to 350°F. Take 2 lbs of potatoes, peel and slice them thinly. Bring 3 cups of heavy cream, a garlic clove, 1 sprig of thyme, salt, and black pepper to a simmer. Then remove from heat. In a baking dish, layer potato slices and pour cream mixture over them, add grated Gruyere cheese on top. Repeat layering until all potatoes and cream are used and cheese tops it. Then place the baking dish in the preheated oven and bake for about 45-55 minutes or until golden brown on top. Allow it to cool for a few minutes before serving.