Caramelised Onion and Mushroom Spread

"Spread this on crusty bread or savoury biscuits, use it as a topping for tartlets or as a delicious spread in sandwiches. Used as a sandwich spread, I simply add something like a slice of roasted red pepper and baby spinach leaves. Or slices of ham. I adapted this recipe from one I found online because I was not satisfied with the gourmet spreads I'd been buying. Well they classified themselves as gourmet but they were, in fact, rather ordinary and also quite expensive! I love the fact that this recipe also has mushrooms in it - and a few other goodies! The original recipe must have been a Birds Eye recipe as it specified using Birds Eye Frozen Sliced Onions. I've slightly increased the mushrooms and garlic as I generally do with recipes and I've added leeks as the combination of flavours from onions, leeks and garlic is just so delicious. And I've also added thyme. Vary the garlic - and any of the ingredients - to suit your taste preferences. I've suggested adding more balsamic vinegar if your onion mixture seems too dry. If like me, you are a bit inexact in the measurement of some of the ingredients - oh, I may as well use all of that! - ;) this would obviously be the easiest way to correct this. Have fun playing with this recipe - and I hope that you enjoy it. I keep meaning to add some chopped nuts, probably walnuts, and must try to remember to do so next time I make this."