Take puff pastry out of freezer and allow to thaw 30-40 minutes until workable.

In a large pan over medium heat cook your vegan butter and onions for 15 minutes. Add garlic and 1 chopped portobello mushroom and continue cooking 5 minutes until mushrooms have softened.

Add spinach, leaves from 2 sprigs (½ tsp dried) thyme and a dash of salt and pepper and cook until wilted.

Place mixture in a sieve and remove as much moisture as possible (if it's too moist the puff pastry will break), I usually use a dish towel or two to squish out the liquid. Add flax and mustard and mix well.

Add rice, diced or shredded vegan cheese, 2-4 more fresh thyme sprig leaves (about ½ tsp dried), salt and pepper to taste and mix well, set aside to cool.

In the same pan cook the remaining 2 whole portobello mushrooms (after rinsing and remove the stems) on each side for 5 minutes, set aside to cool.

Once fillings are completely cooled, preheat your oven to 400ºF/200ºC.

Roll out your puff pastry to between ⅛-¼ inch thick in a rectangle shape, as thin as possible but still being workable and not breakable.

Add half the filling to the pastry in the same rectangle shape, leaving borders around the pastry, then place portobellos on top. Add rest of filling and gently squish down.

Fold over the long edges and squish down, then fold the short edges up, wrapping it like a present. You may find it helpful to dip your finger in water and run this along the seals to help it stick together.

Carefully roll it over and place on a baking tray lined with parchment paper. Add slits in a criss-cross design.

Mix together vegan egg wash and top entire loaf with wash. Bake for 30-35 minutes until golden brown, you may want to broil it for just a bit to get the color you want towards the end.

Allow to cool a bit and then cut into servings!