Seared Filet of Beef with a Rosemary Portabella Mushroom Cream Reduction

Ingredients

1 whole filet of beef (4 to 5 pounds)
2 tablespoons butter
olive oil
1 tablespoon kosher salt
1 tablespoon coarsely ground black pepper
Reduction:
16 ounces mushroom blend cleaned, stemmed and thinly sliced (use shitake, baby bella, white, etc)
¾ shallot, finely diced
1 cup red wine
1 cup beef stock
½ cup heavy cream
1 tablespoon cold unsalted butter
1 tablespoon chopped fresh rosemary, finely chopped

Instructions

Preheat the oven to 500 degrees F. Heat a large fry pan over medium-high heat.
Place the beef on a baking sheet and pat the outside dry with a paper towel. Spread the butter on with your hands. Sprinkle evenly with the salt and pepper.
On high heat, add 2 tablespoons of olive oil to pan and pan sear all sides of roast until brown.
Remove from pan and put in roasting pan. Roast in the oven for exactly 2 minutes for rare and 25 minutes for medium-rare.
Remove the beef from the oven, cover it tightly with aluminum foil, and allow it to rest at room temperature for 20 minutes. Remove the strings and slice the filet thickly.
For the Sauce:
Using same sauce pan from beef. Remove all but 1½ tablespoons of the fat in the skillet and return to high heat. If not enough fat, add some olive oil. Add the mushrooms and shallots, and rosemary, season with salt and pepper. Saute until golden brown and liquid has evaporated. Add the red wine and cook until reduced by half. Add the stock and cook until reduced by half. Add cream. Whisk in the butter and cook for 30 seconds. Taste and season with salt and pepper if needed.