Step 1

Pour 1 bottle root beer into a standard-sized ice cube tray. Carefully transfer to the freezer until frozen, 3 to 4 hours.

Step 2

Whisk cold cream and vanilla in a small bowl until slightly thickened. Cover and place in the refrigerator until needed.

Step 3

Transfer root beer ice cubes into a blender. Add 1 1/2 cups cold root beer and blend until a smooth, thick slush forms, stopping and shaking the blender as needed.

Step 4

Pour into 2 frozen mugs, leaving about 1 inch of room at the top. Spoon vanilla cream over top and serve.