In a small sauce pan, add the olive oil and heat over medium heat. Add the onions and cook until they are translucent, about 5 to 6 minutes. Add the garlic and cook for 30 to 40 seconds until you can smell the garlic. Add the wine, reduce the heat to medium low and cook until half of the wine has been absorbed.
Add the blueberries, allspice and balsamic vinegar and continue cooking for 10 to 12 minutes, stirring occasionally, until thickened. Add the butter and whisk vigorously to break up any remaining whole berries. Remove from the heat and serve either on the side or drizzled over the slices of steak.
WHAT?? Blueberries on steak? Yep, that's what it is and, boy, is it good. But of course, you have to have the right kind of steak. No rib-eye or porterhouse. We are talking Chateaubriand, London Broil, Tri-tip, filet mignon roast. Steaks you have to slice to serve. Really.
I wanted some mushrooms with the steak, so I sliced a Portobello mushroom thinly (3/8') and cooked it in a little olive oil or butter until the slices were limp. A little of the blueberry sauce snuck onto the mushrooms, which was then followed by a LOT of the sauce. Add some steamed asparagus on the side for a truly heavenly meal.