1.5 pounds cremini or shiitake mushrooms, finely chopped
2 large shallots, minced
4 cloves garlic, minced
2 tablespoons unsalted butter
1 tablespoon olive oil
1/4 cup vegetable broth
1 tablespoon balsamic vinegar
2 teaspoons fresh thyme, chopped
1 teaspoon fresh rosemary, chopped
5 ounces fresh baby spinach
1/2 cup walnuts, finely crushed
1 egg, beaten for egg wash
Salt and black pepper to taste
Instructions
In a large skillet, melt the butter and olive oil over medium-high heat. Add the finely chopped mushrooms and cook them for about 10 to 12 minutes. It is very important to cook them until all the moisture has evaporated and they start to brown nicely. This prevents the pastry from becoming soggy later on.
Stir in the shallots and garlic, cooking for another 3 minutes until softened. Pour in the vegetable broth and balsamic vinegar, using a wooden spoon to scrape up any browned bits from the bottom of the pan. Continue to cook until the liquid has completely reduced and the mixture is relatively dry.
Add the fresh thyme, rosemary, salt, and pepper to the pan. Toss in the baby spinach and cook just until it wilts into the mushroom mixture. Remove the skillet from the heat and stir in the crushed walnuts. Transfer the filling to a bowl and let it cool completely, this is a crucial step for a crispy crust.
On a lightly floured surface, roll out one sheet of puff pastry. Place the cooled mushroom filling in the center, shaping it into a neat log. Leave about two inches of space on all sides. Brush the edges with the beaten egg wash and place the second sheet of pastry over the top. Press the edges together with a fork to seal the Wellington tightly.
Preheat your oven to 400 degrees Fahrenheit. Transfer the Wellington to a baking sheet lined with parchment paper. Brush the entire surface with the remaining egg wash and use a sharp knife to gently score a decorative pattern into the top. Bake for 25 to 30 minutes, or until the pastry is puffed and deep golden brown.
