Savory Mushroom & Walnut Puff Pastry

1. Prepare the Portobello Mushrooms

Wipe the portobello mushrooms clean, remove the stems, and slice off any excess rim. Brush each mushroom with olive oil, season generously with kosher salt and black pepper, and sear them in a nonstick skillet over medium-high heat until they are golden brown, about 10 minutes. Set them aside to cool.

2. Prepare the Mixed Mushrooms

Chop half of the mixed mushrooms finely in a food processor and hand chop the other half for texture. Heat 0.5 cups of olive oil in a large skillet over medium heat, and cook the chopped mushrooms in batches until they are tender and caramelized, about 10 minutes per batch. Add the finely chopped shallots, garlic, and rosemary to the skillet, cooking for an additional 5 minutes until fragrant. Pour in the port or balsamic vinegar, soy sauce, and fresh thyme, allowing the liquid to reduce for 3-4 minutes. Stir in the toasted walnuts, then transfer the mixture to a bowl placed over an ice bath to cool.

3. Caramelize the Onions

Melt 3 tablespoons of unsalted butter in a skillet over medium heat, then add the sliced yellow onions. Sprinkle with brown sugar, 1.25 teaspoons of kosher salt, and 0.75 teaspoons of black pepper. Cook the onions for about 5 minutes, then pour in the apple cider. Let the onions simmer until the liquid has evaporated and the onions are deeply caramelized, around 15 minutes. If you like, stir in a tablespoon of aged balsamic vinegar for extra depth.

4. Prepare the Puff Pastry

Preheat your oven to 400°F (200°C) and line a sheet pan with parchment paper. Roll out the puff pastry on a lightly floured surface to smooth out any creases. Spread half of the mushroom mixture over the puff pastry, followed by a layer of caramelized onions. Arrange the seared portobello mushrooms on top, adding the remaining mushroom mixture. Fold the puff pastry over to enclose the filling, sealing the edges with beaten egg. Brush the entire pastry with more beaten egg for a golden finish.

5. Bake the Pastry

Bake the pastry in the preheated oven for 45-50 minutes, or until it is deep golden and flaky. Allow it to cool for 10 minutes before slicing.

6. Prepare the Port Reduction (Optional)

For an optional finishing touch, prepare a port reduction. Heat 2 tablespoons of olive oil in a saucepan over medium heat, then sauté the minced shallot and garlic for about 3 minutes. Add the whole black peppercorns, 1.5 cups of port, vegetable stock, and fresh thyme sprigs. Bring the mixture to a boil, then reduce the heat and let it simmer for 25-30 minutes until reduced by half. Strain the sauce, then whisk in 3 tablespoons of unsalted butter until smooth.

7. Serve the Pastry

Serve the puff pastry sliced into 8 slabs, presenting the golden side up. Drizzle with the port reduction if desired, and enjoy the rich, savory flavors in every bite.