See the 42 Second Version: "Shaking Butter Like A Boss"
Note: This method takes 5-10 minutes, but Dan Rojas with GreenPowerScience found a way to make the butter in under a minute by using a water bottle. Check out his video here:
Step 1: Watch the Video!
WARNING: Use safe practices when handling food to avoid contamination, and only use milk or cream from trusted and approved sources. Shaking cream into butter may result in an amazing workout. Use of video content is at own risk.