By An Edible Mosaic
Pro tip
Add the butter to a large skillet over medium heat. Once melted, add the onion.
This is the onion after cooking 10 minutes.
This is the onion after cooking 20 minutes.
Cook the onion until deep golden in color, about 30 minutes, stirring occasionally. Add a splash of water when it starts to stick to the pan, or when it starts to get too dark. Adjust the heat down as necessary so the onion doesn’t burn.
Once caramelized, stir in the salt and balsamic and cook about 1 minute, scraping up any brown bits from the bottom of the pan. Remove from the heat.