In a large skillet or frying pan heat Olive Oil (1 tablespoon) over medium-high heat to almost the smoke point, add Onion (1 cup); stir and saute 2-3 minutes until caramelized and browned.
Add Chicken Broth (1/4 cup) while stirring and bringing up the bits and pieces from the bottom of the pan.
Add Garlic (1 teaspoon), sauté, and stir for 1 minute.
Add the Boneless, Skinless Chicken Breast (4), cook for 2 minutes per side.
In a small bowl combine Ketchup (3/4 cup), Chicken Broth (3/4 cup), and Brown Sugar (1/4 cup). Stir to combine.
Add the mixture to the skillet or pan and reduce to a simmer.
Cook for 25 minutes or until the internal temperature of the chicken reaches 165 degrees F (75 degrees C).