Heat 2 tablespoons of olive oil or butter in a large frying pan over medium heat. Add your sliced onions and a pinch of salt, bring the heat down to medium-low and saute for about 20 minutes, stirring occasionally. When they are just about done, add in minced garlic and stir until fragrant.
Once onions are looking golden brown, add in balsamic vinegar, maple syrup, coconut or brown sugar, liquid smoke, and Worcestershire sauce. Stir all of this together until the sugar is dissolved.
Turn the heat to high to come to a boil and then turn to medium and simmer until it begins to thicken, about 10-15 minutes. Be sure to taste throughout the cooking process and adjust to your liking. This can be as sweet, tangy, or smoky as you prefer!
Once cooled, I store this in a sealed jar in my fridge for about a week. Don't worry if the butter or oil starts to congeal in the fridge. Just take it out and let it come to room temperature before serving.