In a large bowl add the chicken thighs and olive oil. Mix that together with your hands until combined.
Then sprinkle over the seasoning blend and really get the seasonings all over both sides of the chicken and under the skins.
Let the seasonings marinate in the bowl on the counter for 30 minutes to ensure that the seasonings penetrate through the skin and the chicken and let it come to room temperature
In a cast iron on medium-high heat add the vegetable oil and butter. Make sure your skillet is hot before adding in the chicken.
Once it's hot add the chicken thighs skin side down and DON'T MESS WITH IT! (do not move the chicken before you let it brown, this is very important)
Saute the chicken on each side for about 5 minutes until browned.
Flip the chicken and brown on the other side for another 5 minutes. Continue the process until all of the chicken thighs are browned on both sides.
Once all the chicken thighs are nice and browned add them into a 9x13 baking dish and pour the leftover oil from the cast iron skillet over the chicken thighs.
Place a piece of aluminum foil loosely over the baking dish and place that in the oven at 350°F for 20 minutes.
After 20 minutes remove the baking dish from the oven and remove the aluminum foil.
Baste the chicken with the juices from the pan and place the baking dish back in the oven at 350°F for 30-40 more minutes or until the chicken reaches the internal temperature of 170°F.
Serve over mashed potatoes and steamed broccoli.
Pour the juices from the bottom of the pan over the broccoli , mashed potatoes, and chicken thighs & enjoy!