Roast Beef with Bourbon Mushroom Sauce

Name: Roast Beef with Bourbon Mushroom Sauce
Ingredients: 1/4 cup coarse sea salt; 1/4 cup coarse cracked black pepper; 2 to 3 tablespoons grapeseed oil, for searing; 1 whole Beef Striploin, trimmed with some fatback remaining; Bourbon Mushroom Sauce, recipe follows; 5 tablespoons butter, divided; 1 tablespoons garlic, minced; 1 cup cremini mushrooms, sliced; 1 cup onion, finely diced; 4 tablespoons all-purpose flour; 1/4 cup bourbon; 3 cups beef stock; Salt; 1 tablespoon cracked black pepper; 2 tablespoons chopped fresh parsley