Melt the butter and olive oil in a large skillet over medium heat.
Add the chopped onion and sauté until translucent, about 5 minutes.
Stir in the minced garlic and cook for an additional minute until fragrant.
Add the sliced morel mushrooms to the skillet and cook for about 5-7 minutes, or until they are tender and browned.
Pour in the bourbon and let it simmer for 2-3 minutes, allowing the alcohol to cook off slightly.
Reduce the heat to low and stir in the heavy cream, Dijon mustard, salt, and black pepper.
Simmer for another 5-10 minutes, stirring occasionally, until the sauce thickens to your desired consistency.
Remove from heat and garnish with fresh parsley before serving.