This can stand alone with a very simple side like rice to catch the extra juices. Myself, I’m a veggie lover and so I make a simple side salad or steamed carrots.
Note about the balsamic vinegar, you don’t have to break the bank but do pick one that has a nice well rounded flavor. In making the glaze those flavors will be concentrated and made a little sweet, so it’s best to start out with a decent quality vinegar.
Note about the filling, this can be made up to two days ahead of time. Just store in the fridge in a airtight container until you are ready to stuff the steak. Any longer than two days and I find it loses it’s bright flavor and color.