To temper heavy cream you gradually increase the temperature of the cream by adding a small amount of some hot liquid like sauce or broth to the cream.
The process of tempering the heavy cream prevents the cream from separating or curdling when it's added to a hot dish or hot food.
When tempering the heavy cream, start by turning down the heat on the hot liquid that you're adding the heavy cream to.
Then add a small amount of the hot liquid to the heavy cream by taking a tablespoon or two of the hot liquid and then add it to the heavy cream in a separate bowl.
Next mix the heavy cream and hot liquid thoroughly by stirring it well.
Then repeat the process and gradually add some more hot liquid to the heavy cream, while stirring continuously, until the heavy cream has warmed up and is mixed well with the hot liquid.
You can also take about half a cup of the hot broth and then slowly add the heavy cream to the hot broth while stirring constantly.
If you want to quickly bring heavy cream to room temperature you can microwave the heavy cream in a microwave safe bowl, with 10 second intervals, stirring between each pulse.
You can also put the heavy cream in a bowl and place the bowl in a larger bowl of warm water for 5 to 10 minutes.
Or you can simply leave the heavy cream on the counter covered for around an hour to bring the heavy cream to room temperature.