For the Pork Tenderloin:
2 1-pound pork tenderloins
kosher salt
ground black pepper (ideally 16 mesh)
For the Creamy Mushroom and Bourbon Sauce:
2 tablespoons olive oil
4 tablespoons butter
1 pound white mushrooms, thinly sliced
1 yellow onion, diced
8 cloves garlic, minced
1 teaspoon Dijon mustard
½ teaspoon Italian seasoning
1 teaspoon fresh lemon juice
½ cup bourbon
1½ cups heavy cream
kosher salt, to taste
ground black pepper, to taste
1–2 tablespoons finely chopped fresh parsley
Set up your Big Green Egg for direct grilling and preheat it to 375°F. While it preheats, trim the pork tenderloins of any excess fat and silver skin. Season the trimmed tenderloins with salt and pepper. Let them sit at room temperature until your Big Green Egg is ready.
When the Big Green Egg has preheated and the temperature is stable, place the tenderloins on the grill grate and cook them for 10 minutes. Flip them and place a 12-inch cast-iron skillet on the grill grate to preheat while the pork finishes cooking, which will take 10 minutes. When the pork measures 140°F internally, remove it from the Big Green Egg and allow it to rest for 20 minutes.
While the pork is resting, make the creamy mushroom and bourbon sauce. Add the olive oil and butter to the preheated cast-iron skillet. Once the butter has melted, add the mushrooms and onion. Sauté for 10–12 minutes, until the mushrooms have released their liquid, and the onion is soft and dark yellow in color. Using heat-resistant gloves, remove the cast-iron skillet from the Big Green Egg and stir in the garlic, mustard, Italian seasoning, lemon juice, and bourbon. Mix the ingredients well and return the cast-iron skillet to the Big Green Egg. Pour in the heavy cream and cook the sauce for 3–5 minutes, or until the sauce has reduced and thickened. Season it with salt and black pepper, then stir in the parsley.
Slice the pork tenderloins and serve them with a generous amount of the creamy mushroom and bourbon sauce.