Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper.

In a bowl, mix the softened goat cheese, cream cheese, fresh thyme, parsley, garlic powder, and black pepper until smooth. Set aside.

Heat butter and olive oil in a skillet over medium-high heat. Add the sliced shallots and sauté for 2-3 minutes until softened.

Add the sliced mushrooms. Let them cook undisturbed for a minute to brown, then stir and cook for another 5-7 minutes until deeply golden and their moisture has evaporated.

Deglaze the pan with a splash of white wine or balsamic vinegar, scraping up any browned bits. Remove from heat and let cool slightly.

Unroll the cold puff pastry sheet and cut it into 6 equal squares. Place them on the prepared baking sheet.

Lightly score a 1/2-inch border around the inside edge of each pastry square with a knife. Prick the inner center square several times with a fork.

Spread a generous dollop of the goat cheese mixture inside the scored border of each tart. Top with the cooled mushroom and shallot mixture.

Brush the exposed pastry borders with the egg wash.

Bake for 15-20 minutes until the pastry edges are puffed and deeply golden brown. Garnish with fresh herbs and serve warm.