Cow in a Jar

The Cow in a Jar is a genius invention based on the Milk Jar.

Inside is a tiny cow that will continuously produce milk over time.

Check the Cooking Table for more information on multi-block Kitchens.

Crafting (in-world)

If the above image is not clear enough, I've also made a short instructional video visualizing the process:

Drop an anvil block on a cow above a milk jar.

Right-click with a bucket of milk to put milk into the milk jar. Right-click with an empty bucket to take it back out.