Step 1

Pour the milk into the jar: Fill your jar with as much milk as you normally use in your coffee, but no more than halfway full so there's room to make some foam.

Step 2

Shake the jar with the lid on: Screw on the lid. Shake the jar as hard as you can until the milk is froth and has roughly doubled in volume, 30 to 60 seconds.

Step 3

Microwave for 30 seconds: Take the lid off the jar. Microwave uncovered for 30 seconds. The foam will rise to the top of the milk and the heat from the microwave will help stabilize it.

Step 4

Use the foam: Pour the warm milk into your coffee and spoon the milk foam on top.