Preheat the oven to 375.

Butterfly the flank steak. You can have your butcher do this or you can do it at home. To do it at home, with the steak lying flat and the long side facing you, use a sharp knife to slice through the meat horizontally being careful to keep the meat in two even halves. You aren't going to slice completely through the meat, you want to open it like a book. Once the meat is butterflied season the inside with salt and pepper.

In a large skillet over medium heat cook pancetta until it crisps up. About 5 minutes. Remove and set aside.

In the same skillet heat 2 tablespoons of olive oil. Add garlic and mushrooms and cook for 5 minutes. Add the spinach and cook just until it wilts. Remove from heat.

With the steak lying open like a book, layer the spinach and mushrooms mixture , then top with pancetta and then goat cheese.

Next gently roll the steak starting at the end closest to you and rolling away. Use the kitchen twine to tie the steak in 1-2 inch intervals. This is just to ensure that you don't lose any stuffing while it cooks.

Over med-high heat in the same skillet you used for the spinach, sear the steak on each side. 5 minutes per side.

Place in a baking dish and bake for 25-30 minutes or until the internal temperature reaches 130 degrees.

Remove from the oven and cover. Let rest for 10 minutes, then slice. Resting is very important because it allows the meat to retain the juices leaving it very tender.