Grab a medium pan and add the olive oil. Once hot, add onions and garlic. Sauté until they soften and become aromatic.
Add remaining ingredients and cook until the sauce thickens (about three minutes). Then, remove it from the stove and set it aside to cool.
Add oil to the grill so that the chicken doesn’t stick. Dip the chicken in the homemade sauce until it’s fully covered and add to the grill. Cook for 10-15 minutes, flipping halfway through. Shift the chicken into the pan and simmer with the sauce for an additional 10 minutes, flipping halfway through.