1 2-pound beef tenderloin
sakt and freshly ground black pepper to taste
3 T extra virgin olive oil
3 oz. pancetta, chopped
2 shallots, peeled and minced
1/4 cup Balsamic vinegar or Modena
1 1/2 cups veal or light beef stock
6 cups baby spinach leaves
Season the beef liberally with salt and pepper. Heat a large saute pan or skillet over medium-high heat. Heat the olive oil and brown the tenderloin on all sides. Transfer to a cutting board and let cool. The beef should be very rare, cook longer if this is a problem.
Add the pancetta to the pan, cook over medium heat for 4 to 5 minutes, or until golden brown. Add the shallots and cook until softened, about 2 minutes. Add the Balsamic vinegar, deglazing the pan. Add the stock and cook over high heat until reduced by half.
Slice the steak very thin. Divide the spinach leaves evenly among 6 plates, fan the beef slices evenly over the spinach and spoon the warm sauce over all. Salt and pepper to taste and serve immediately.