My butter is always too hard or too soft. If it's been in the fridge, it's too hard. If it's left out, it's practically melted. I propose an external butter container that you plug into your refrigerator, composed of some insulated conductive metal which will keep the butter at the perfect temperature, so it will melt on toast and cut easily, but not be totally melted to start off. The fridge would have plugs enabling the heat from the container to transfer into the fridge, cooling the container. Perhaps the area in the fridge where the plugs go would be sealed off so you could control the temperature of the external devices. This could be used for other things, such as cakes or whatever.
Reward: the finished product