Season both sides of the chicken with garlic powder, salt, and pepper.  In a large skillet, heat the olive oil and cook the chicken on medium heat until fully cooked and browned on both sides.  Remove chicken and set aside.

In the same skillet, add the butter and onions.  Sautee the onions on medium/low heat.  After about 10 mins, add the sugar.  Continue to sautee the onions until they're caramelized (about 5 - 10 mins).  Add thyme, red pepper flakes, and balsamic vinegar and continue to sautee for another 5 mins.

Slowly pour in the chicken broth and while whisking it into the onion mixture.  The broth with deglaze the pan and collect all the yummy chicken bits.  Turn the heat up to high/medium and let it simmer and reduce for 3 or 4 mins.  

Reduce the heat to low and whisk in the heavy cream.  Be sure the heat is low because if the cream starts boiling too fast it will cause the sauce to separate.  When the sauce reaches a simmer, it's done.