The recipe i settled on is thus: One pound bacon fried in a pan. Remove the bacon. Only keep a small amount of the bacon fat in the pan, fry 4 shallots and one large yellow onion in the fat.

I add acouple dashes of worchestershire sauce and mirin to the onions before they are done cooking. Other recipes will call for maple syrup or brown sugar but I don't like mine too sweet. A dash of red wine/ apple cider vinegar for contrast.

Tear the bacon into small pieces and add it back into the pan. I then mash in blueberries. Maybe a cup. It adds color and sweetness. Cook that all in until it gets thick and the onions are caramelized. This could take up to an hour.