Cook onions in a few tablespoons of oil or grease for a few minutes. Add garlic. Cook a few more minutes. Add some wine, and scrape the pan with the wine.
Add a pile of blueberries. Have a glass of wine while the blueberries cook. After all, the bottle is already open, no sense in letting it sit. When everything is all bubbly and thick, throw it in a blender and grind it up. Add salt and pepper to taste.
This glaze is excellent on grilled pork or shrimp.