Starting with the long side of your flank steak, cut it in half carefully, but don’t cut all the way through to the other end (butterfly it). You want to cut it and open it like a book. Once it’s cut and open like a book, place a piece of plastic or parchment over it and pound it to uniform thickness – about ¼ of an inch thick.
In the largest skillet you have (must fit the rolled up steak), pour 1 – 2 T oil in the pan over medium low heat. Add your shallot, garlic, and mushrooms and cook for 5 minutes. Season them with salt and pepper.
Add the mushroom mixture to the flank steak, leaving 2 to 3 inches of open space on one of the long ends.
Add the red peppers on top of the mushrooms. Then add the prosciutto slices all over the red peppers. Then add your spinach all over the prosciutto. Next sprinkle the blue cheese all over the spinach.
Starting with the long end (not the end that you left 2-3 inches of space), roll up carefully.
Now tie kitchen twine around your roll about every 2 inches. Salt and pepper and sprinkle the smoked paprika all over the outside of the roll.
Pour 1- 2 T oil back in the skillet and turn the heat to medium high.
Sear your roll on all sides until browned – it takes about a minute each side.
Transfer your skillet to the oven and cook for 20 minutes (for medium).
After the 20 minutes is up, take it out and tent your steak with alluminum foil. Let rest for 10 minutes. For steak done more than medium: cook in the oven for 30 minutes, tent steak and let rest for 10 minutes.
To serve: cut off the twine and slice in ½ – 1 inch slices and enjoy!