1 Tablespoon vegetable oil
4 medium white onions, thinly sliced (about 8 cups)
2 generous pinches Kosher salt
10 grinds fresh black pepper
½ cup sugar
2/3 cup balsamic vinegar
Heat vegetable in a large skillet over medium heat until it slides easily across the pan.
Add the onions, salt and pepper and cook, while stirring occasionally, for 20 minutes until the onions are soft.
Add the sugar and reduce the heat to medium-low. Cook the onions, stirring frequently, for 10 minutes.
Add the balsamic vinegar and reduce the heat to low. Continue cooking the onions, stirring occasionally, for one hour until they are very soft and dry. Serve warm or at room temperature.