Preheat your oven to 425°.

Heat a couple tablespoons of olive oil in a large skillet. Sauté the rapini, onions and garlic until the rapini starts to wilt (about 5 minutes) and add in the mushrooms, seasoning, and bread. Continue to cook until everything is soft and wilted and the bread is lightly browned but not crispy, about 5 minutes. Allow to cool about 10 minutes then stir in the parmesan.

Meanwhile, place your steak between two sheets of parchment paper on a cutting board. Use a meat mallet to flatten it to a uniform ¼ inch thickness. If your flank steak is unusually thick, you can butterfly it—slice it down the middle horizontally leaving a about ½ inch connected on the end and then flatten it.

Remove the parchment and place a length of kitchen twine under the meat. Spoon the filling down the center of the steak. Wrap the sides around the filling and secure with kitchen twine. I use one long string, wrap the whole thing and tie it on both ends. You could also tie it shut in sections. Either way, you want it to be tied tightly and for the two sides of the meat to touch, fully covering the filling. It’s possible you may have filling leftover. You can eat the filling leftover as a reward for cooking.

Sear the steak on both sides in a hot pan—I used the same pan I used to make the filling. Remove it to a baking dish long enough for it to lay flat and drizzle with a tiny bit of olive oil. Sprinkle with salt and pepper.

Bake for 30 minutes. Remove from oven and allow to cool for 5 minutes. Cut it into about 8 half inch slices. Serve immediately.