Make frozen orange juice cubes:
Squeeze about 6 to 8 large, sweet juicing oranges, such as Valencia, into a large measuring cup. With a fine mesh strainer, strain pulp. Pour into ice cube trays or large ice cube molds. Freeze overnight.
To blend frozen mimosas:
Combine orange juice cubes with bottle of very cold sparkling wine in a blender or Vitamix and blend until smooth.
Serve immediately with straws.