Ingredients

• 1 1/3 cups roughly chopped red onion (about 1 medium onion)

• 1 1/4 cups red wine vinegar

• 3/4 cup (6 ounces) cream sherry 

• 3 tablespoons granulated sugar

• 1 1/4 teaspoons kosher salt, divided, plus more to taste

• 1 cup unsalted roasted cashews, roughly chopped

• 1/4 cup cream cheese, softened

• 1 (17.3-ounce) package frozen puff pastry sheets, thawed

• 10 1/2 ounces fresh shiitake mushrooms, stemmed and cut into 1/4-inch slices (about 2 2/3 cups)

• 2 tablespoons olive oil, plus more for serving

• Grated Parmesan cheese and thinly sliced scallions, for garnish