1 tablespoon unsalted butter
1 1/2 cups chopped mushrooms
1/2 cup diced onions
1 teaspoon rosemary
2 teaspoons minced garlic
2 teaspoons Worcestershire sauce
kosher salt and black pepper
1 lb butterflied flank steak
1 1/2 cups fresh spinach
1/2 cup seasoned breadcrumbs
1/4 cup melted unsalted butter
Toothpicks for securing
Preheat oven to 350 degrees. Add olive oil and butter to medium sized pan over medium high heat. Once both melt together, add mushrooms, onions, rosemary, and salt and pepper to taste, stir and cook until tender. Next add the minced garlic and cook for an additional minute, making sure not to burn it. Add in Worcestershire sauce, stir together and cook for an additional 1-2 minutes, then set mixture aside while you prepare the steak. Lay butterflied steak on a cutting board and season with salt and pepper on the outside of the steak then turn over. Spoon mushroom mixture in an even layer across the steak. Next arrange spinach and sprinkle breadcrumbs evenly over the surface of the mushroom mixture. Drizzle half of the butter over the breadcrumbs. Starting at the very bottom of the steak, carefully and tightly roll steak, and secure seam with toothpicks to hold it together. Place the rolled steak in the center of the baking pan and brush the top of it with the remaining butter. Bake until the probe inserted into the steak reaches an internal temperature of at least 145 degrees F, around 40 minutes. Your steak will be medium to medium well around this temperature. If you prefer it well done, continue cooking until it reaches internal temperature of 155. Remove rolled steak from oven and allow it to sit for 10 minutes. Cut the steak into 1 inch thick slices, remove toothpicks, and serve with easy roasted Brussels sprouts if desired.