Reduce the cream. Add cream to a non-reactive saucepan. Turn the heat on to low and let the cream come to a simmer. Let the cream simmer for about 20 - 30 minutes or until reduced by half. Don't stir during this process. A spoon will upset the whey from the bottom of the pan and upset the process to thicken the cream. Remove from heat until ready to use.
In the meantime, using a large fry pan, heat butter and saute the mushrooms over medium high heat until the mushrooms give up their water and begin to caramelize. They'll start to turn golden. This will take about 5 - 10 minutes.
Deglaze the mushrooms by adding white wine. Stir to release all of the brown bits of flavor from the bottom of the pan. Continue to cook until the wine has almost cooked off.
Sprinkle the mushrooms with flour and paprika. Stir well and swiftly to combine.
Add the stock while whisking vigorously to remove any lumps and bring to a simmer. Simmer on low for 20 minutes.
To finish the sauce, add the reduced cream to the sauce and simmer just enough to blend and thicken. About 5 minutes.
Set the sauce aside and sear the steaks. Pat the steaks dry with a paper towel and season with salt and pepper. Heat an oven safe fry pan over medium high heat. Once the pan is hot, add the oil. Once the oil is shimmering add the steaks to the pan. Let them cook without moving them. Cook for about 5 minutes or until the steaks will release from the pan without sticking.
Turn the steaks over and let them sear for another 2 - 3 minutes. Transfer the pan to a 400 degree oven to finish. Use a digital real meat thermometer to determine temperature.
To serve, slice the steak thin and top with a ladle of the mushroom cream sauce.