Heat the olive oil in a large skillet over high heat.
Sear the chicken breasts, skin-side down, for 3-4 minutes. Don't crowd the pan, you may have to do multiple batches.
After the chicken is seared, place it in a 9x13 (or similar) baking dish. DO NOT wash the skillet you seared the chicken in, you will need this later on in the recipe.
Bake for 20-25 minutes, or until the thickest part of the chicken registeres 160ºF on an instant-read thermometer. This time may vary depending on the size of the chicken breasts you use.
For the Sauce
After you've removed the chicken from the oven, it will need to rest for 10 minutes. While the chicken is resting, make this quick sauce.
In the same pan you used to sear the chicken and didn't wash, heat 1 tablespoon of olive oil over medium heat.
Add the onion and cook until it's translucent, about 5 minutes.
Add the white wine and scrape up all the browned bits on the pan as it evaporates.
Add the chicken broth and bring to a simmer.
Simmer until the sauce is reduced by about half, about 5-8 minutes.
Once the sauce is reduced, stir in the butter and fresh parsley off heat.