Set tenderloin steaks out to come to room temperature. Pat dry with paper towels. 

Slice larger mushrooms in half. Cut onion into bite sized pieces.

Toss mushrooms and onion with olive oil, 1/2 teaspoon of salt and 1/2 teaspoon of pepper in a bowl.

Thread vegetables onto skewers.

Melt butter in a small pan over low heat. Adde minced garlic and cook, stirring often until garlic is toasted. Watch constantly, so that the garlic doesn't burn.

Stir in bourbon.

Remove from heat and cool about 5 minutes. 

Mix in brown sugar, green chile powder and remaining salt and pepper, stirring until brown sugar is melted.

Cook steaks and vegetable skewers over indirect fire with the grill closed about 5 minutes.

Flip the steaks and cover each steak with butter mixture.

Spoon any excess butter over the mushroom skewers.

Continue to cook about 7- 10 minutes with the grill closed. Check steaks with a digital thermometer cooking to desired doneness, about 135° for medium.

Remove from grill and allow steaks to rest about 10 minutes before slicing.

Serve steaks with mushrooms and onions.