Peel and thinly slice the onions and shallots.

Add the olive oil to a Dutch oven or heavy bottomed pot. Add the onions, shallots, and garlic.

Cover and cook for 20 minutes, stirring occasionally.

Remove the lid and add red wine, balsamic vinegar, and brown sugar.

Cook for another 30 or so minutes, or until the onions are caramelized. Add fresh thyme and season with salt and pepper. If you still have large cloves of garlic remaining, use a fork to mash them up and stir into the jam.

This jam keeps for two weeks in the fridge.