Heat the cooking oil in your saucepan over medium heat. Let it warm up for about a minute.

Add the diced yellow onion and cook for about 10 minutes. Stir every few minutes until the onions get soft, slightly brown, and see-through. This step makes the flavors really good, so don't rush it.

Pour in the apple cider vinegar, malt vinegar, water, and ketchup. Stir everything together well. The mixture will look thin right now, but it will thicken up as it cooks.

Add the molasses, chipotle peppers with some of their adobo sauce, dark soy sauce, brown sugar, and honey. Stir until everything blends together. The sauce will start smelling amazing at this point.

Sprinkle in the onion powder, garlic powder, and black pepper. Stir again to make sure all the spices get mixed in evenly.

Turn the heat down to low or medium-low and let it simmer gently for 25 to 30 minutes. Stir every few minutes so nothing sticks to the bottom. The sauce should bubble softly, not boil hard.

Take the pan off the heat and pour the sauce through a fine mesh strainer into a bowl. This removes the onion pieces and chipotle bits to make the sauce smooth. Press the solids with a spoon to get more liquid out.

Let the sauce cool down before putting it in a clean bottle or jar. Store it in the fridge.