Preheat your oven to 350°F (180°C) and line a baking sheet with parchment paper.

Melt 2 tablespoons of unsalted butter with 1 tablespoon of olive oil over medium heat in a large skillet. Add 1 chopped yellow onion and sauté for about 5 minutes until soft.

Stir in 2 minced garlic cloves and 8 ounces of sliced cremini mushrooms. Sauté for another 8 minutes until mushrooms brown and moisture evaporates.

Reduce heat to low, add 4 ounces of cream cheese and 1/4 cup of grated Parmesan cheese. If using dry white wine, add it now. Stir until creamy. Fold in 1 cup of grated Gruyère cheese.

Unroll a sheet of thawed puff pastry and cut diagonal strips about 1 inch wide on both sides, leaving a solid strip in the middle.

Spread the creamy mixture down the center of the puff pastry. Fold edges over the filling alternately to create a braid.

Brush the braid with 1 beaten egg for a golden crust. Transfer to baking sheet and bake for 20-22 minutes until golden brown.

Remove from oven and cool for about 10 minutes. Garnish with chopped parsley before serving.