Once you soften scallions and tomatoes, you will add flour to pan and whisk to combine. This will help thicken the sauce.
Now add heavy cream, wine and seasonings!
Lastly, bring the mixture to a boil and then reduce heat to simmering point.
How to add cheese to creamy chicken pasta
Once you reduce the heat, add ½ cup of shredded Parmesan cheese. It’s important to REDUCE THE HEAT before adding the cheese to avoid clumping

In order to incorporate Parmesan well, make sure to use a whisk. Or mix with a wooden spoon until you have a smooth mixture.