Chop the mushrooms. (Optionally, reserve 3-4 large mushrooms to place in the center).
Heat 1 tbsp oil in a large frying pan. Add the onions and fry until lightly browned, about 3 minutes. Add the mushrooms, season with salt and pepper and fry until lightly golden, about 5 minutes. Then lift the mushrooms out onto kitchen paper to drain.
Place the pan back on the heat with the rest of the oil. Roast the garlic for a few seconds, add the spinach and cook for 2-3 minutes until wilted. Then place the spinach into a large sieve to drain and squeeze thoroughly. (Or simply thaw frozen spinach, and squeeze).
Combine fried mushrooms and onions with the cooked rice, season again to taste, add mustard (and optionally chopped walnuts and vegan cheese), stir to combine and place this mixture and the spinach in the refrigerator to cool completely.
Assemble the Loaf:
Preheat the oven to 390°F (200°C).
Place the puff pastry sheet on a baking tray lined with parchment paper. Spread the spinach over the middle of the pastry, making sure to leave a border at the edges. Place the mushrooms on top of the spinach. Top with the remaining filling and thyme, and press a bit together.
Carefully roll the pastry over the top of the filling so you have a loaf. Press down to seal the edges. Roll over the loaf so that the seams are on the bottom.
Gently cut little slits using a sharp knife (but do not cut all the way through) and brush with a little plant-based milk.
Bake the Wellington for approx. 20 minutes, until golden, puffed and flaky.
Serve and enjoy immediately! ?
This Wellington tastes best when baked and served immediately. Anyways, if you have any leftovers, you can bake and reheat it the next day in a preheated oven for approx. 10 minutes.
It’s a versatile recipe, so you can add additional ingredients to your wish (if there's enough room). But please make sure that the filling is dry enough and completely cold before wrapping it in the vegan puff pastry. Otherwise the pastry is going to get soggy and will tear when you want to wrap up your wellington. If the filling is still too moist, simply add 2-3 tablespoons of oats or ground flaxseeds that will soak the excess moisture.