In a large ziplock bag, combine the cranberry jelly, balsamic vinegar, sliced onion, minced garlic, and rosemary. Add the butterflied flank steak, ensuring it's well coated. Seal the bag, removing excess air, and marinate in the refrigerator for at least 3 hours or overnight.

While the steak is marinating, in a mixing bowl, combine softened cream cheese, diced cranberries, chopped shallot, blue cheese, chopped walnuts, and freshly cracked black pepper. Stir until smooth and well blended.

After marinating, remove the flank steak from the fridge and carefully butterfly it if you haven’t already. Use a meat mallet to pound it to an even thickness, about 1/2 inch.

Spread the creamy cranberry filling evenly across the pounded flank steak, leaving a small border around the edges. Roll the steak tightly to enclose the filling and secure it with kitchen twine.

Once chilled, roll the stuffed flank steak in a mixture of cracked black peppercorns. Heat a skillet over medium-high heat, and add olive oil. Sear the stuffed steak for about 2 minutes on each side.

Preheat your oven to 350°F (175°C). Transfer the seared flank steak to a baking dish and bake for about 20 minutes, checking for an internal temperature of 130-135°F for medium-rare.

After baking, let the steak rest for 10 minutes on a cutting board. Slice into pinwheels to showcase the filling and serve warm.