Heat a large skillet or medium saucepan over medium heat.
Add the butter.
Once butter is melted, add the red onion. Cook until translucent, approximately 3-4 minutes.
Add the bourbon and reduce by about half at a simmer, approximately 3 minutes.
Stir in the heavy cream and blue cheese crumbles. Cook until the sauce starts to thicken, approximately 3-5 minutes. Make the sauce as thick (by cooking the sauce down) or as thin (by adding cream) as you like. It will continue to thicken a little as it sits and cools.
Add additional blue cheese or bourbon as desired. Season to taste with salt and pepper.
If you add bourbon at any point, you can continue to cook the sauce to cook off the alcohol in the bourbon.This sauce is great on steaks, chicken, veggies, and more! Try it out on our Bacon and Bourbon Blue Cheese Potato Skins