Add the oil and butter to a deep skillet over medium-high heat. Once the butter has melted, sauté the chopped onion for about 4 minutes until it becomes translucent.

Incorporate sliced cremini mushrooms into the skillet and cook for an additional 5 minutes, stirring occasionally until they are tender and browned.

Reduce the heat to medium and stir in minced garlic, cooking it for about 30 seconds until fragrant but not burnt.

Pour in chicken or vegetable broth along with heavy cream and uncooked potato gnocchi into the skillet. Stir well to combine all ingredients thoroughly before allowing them to bubble gently.

Let it cook uncovered while stirring frequently until the gnocchi has softened and the sauce thickens considerably—approximately 7 minutes. Adjust heat as necessary to prevent excessive bubbling.

Once cooked, stir in softened Boursin cheese until it melts completely into the sauce. Remove from heat, season with salt and pepper as needed, and garnish with fresh chopped parsley if desired before serving hot.