Heat the chicken broth and season it with sea salt and black pepper. Melt two-thirds of the butter in a large pot, and sauté the onions and celery overmedium-low heat for about 20 minutes, or until they have slightly browned. Add the rice, and stir until they are coated with butter. Increase the heat and add 500ml of the wine gradually, allowing the rice to absorb it slowly. Then gradually add the warm broth, stirring constantly, and only adding more broth once the previous portion has been absorbed. When all the broth has been used and the rice is nearly cooked, add the remaining wine gradually while still stirring. The rice will now have taken on the color of the wine. Stir in half of the Parmesan and the remaining butter, and season to taste with salt and pepper. Avoid stirring too vigorously. Serve the risotto with the rest of the Parmesan and a spoonful of crème fraîche, if desired.