Electric butter dish.

I saw this in a charity shop. Think it was £4.99


I looked it up, they don't seem available to buy new now.

https://www.amazon.com/Alfille-Butter-Wizard-Temperature-Controlled-Dish/dp/B001ETYH0U/ref=cm_cr_arp_d_product_top?ie=UTF8

Read the reviews though. 

Here is a video 
https://www.youtube.com/watch?v=8kt18wO386Q