Butter + oven
This ancient method allows butter to be stored for 1-3 years. Place sterilized jars onto a baking sheet, and put the butter inside them. Bake the butter in the oven (230°F or 110°C) for 15-20 minutes. Then add more butter into the jars, screw the lids, and give it another 45 minutes in the oven. Now your butter is ready! Cool it down, and put it on a shelf.