I take it out of the freezer leave it at room temp for a few hours, often overnight and then pulse it in a food processor until it has emulsified. Then I transfer it to a container and chill it for an hour or so, stir - because it will separate a bit but then treat it like fresh.
The process is similar to the "cream makers" that the Brits used to combine milk and butter to make cream.
I should add that mostly I get Manufacturing Cream in half gallons and freeze that. Because it is not ultra-pasteurized, it does not keep as long. Since I use it mostly for making butter and cheese I do not want the ultra-pasteurized because it does not form nice curds without some doctoring - adding calcium chloride...
