Durgol Espresso Decalcifier

To use a French-style butter keeper, pack butter into the cone-shaped lid, or bell. Then add water to the base, so that it's about one-third full (use salted water for unsalted or low-salt butter). When the inverted bell is in place, the water creates a seal that keeps oxygen away from the butter. Contact with oxygen is what makes butter rancid, so the French butter "bell" keeps butter perfectly fresh, while keeping it soft.