Fry your steak as normal.
While the steak is cooking, In a separate pan, fry the mushrooms with a knob of butter and season with pepper.
Once the steak is cooked, put it to one side to rest and collect any juices from the steak.
Move the mushrooms in to the steak pan and using the cream, deglaze the pan of any burnt steak and allow thickening on a high heat to occur but still mixing frequently to avoid burning the cream, pouring any juices from the steak in to the mix.
Serve and Enjoy.