In a saucepan, heat up the olive oil. Add the pancetta and cook until the fat has been rendered down.
Place the flour in a shallow bowl or dish. Dredge the beef in the flour, shake off any excess flour, and add the beef to the hot pan. Sear the beef, stirring well so that all sides are browned. Add the sage, thyme (without the stem), and salt, to taste, to the saucepan. Deglaze the pan with the sherry and stir to pick up any brown bits. Once the sherry has reduced, add a couple ladles of vegetable broth and let reduce. Continue stirring and add the chopped chocolate. Once the chocolate has completely melted, add a few more ladles of vegetable broth.
Allow to cook for 1 hour on medium heat, adding more vegetable broth, if necessary.