In a large, heavy bottomed Dutch oven over medium heat combine the butter and the onions and cook, stirring occasionally until the onions begin to sweat, about 10 minutes. Add the garlic, thyme, salt and pepper and continue to cook, stirring frequently, until the onions begin to caramelize, about 30 minutes.

Once the onions have caramelized, add the balsamic vinegar and honey and continue to cook, stirring occasionally, over medium heat until almost all of the liquid has evaporated.

Remove from heat, taste the onions to check for seasoning. If necessary add more salt and pepper. Allow onions to cool. Serve warm or at room temperature.

The balsamic onions can be stored in an airtight container in the refrigerator for up to 1 week.