Preheat the oven to 375 degrees F.

Season the beef tenderloin roast generously with salt and pepper.

Heat 1 tablespoon grapeseed oil in a large skillet over high heat. Add the beef to the skillet and cook, turning occasionally until the beef is brown on all sides, about 5 minutes. Transfer the beef to a baking sheet. Roast in the oven until a thermometer inserted into the center of the beef registers 120 degrees F for medium-rare, about 35 minutes. Transfer the beef to a cutting board and let rest 10 minutes.

In a large skillet, heat 2 tablespoons grapeseed oil over medium-high heat. Add the mushrooms and saute until browned and lightly crisp.

In a separate skillet, over high temperature, brown the chopped bacon until crisp. Remove the bacon from the skillet and set aside. Pour out most of the bacon fat, reserving some in the pan. In the same pan, heat the bacon fat over medium-low heat. Add the onions and cook the onions until soft and cooked through, about 8 minutes.

In a large saucepan, combine the cooked mushrooms, bacon, onions, and cream, and bring to a simmer over medium heat. Simmer for 15 minutes, or until the cream thickens. Stir in the chopped parsley (reserving some for garnish), and season with salt, and pepper, to taste.

Thinly slice the beef tenderloin and transfer to a warmed serving platter. Pour the warm mushroom gravy over top and garnish with chopped parsley.