400gramsmixed mushroomscut into 2cm (3/4 in.) pieces
½medium butternut squashpeeled and cut into 2cm (3/4 in.) pieces (about 300g)
Start by making the caramelised onions, and take the pastry out to thaw if needed. The onions need two hours plus chilling time and the pastry will need at least four hours to thaw.
Preheat the oven to 200C (400F).
Add the mushrooms, squash, walnuts (if using), olive oil, sage, rosemary, salt, pepper, and paprika to a roasting dish.
Mix until the vegetables are coated, then bake for 25-30 minutes, or until reduced by about half and the vegetables have golden edges. Set aside to cool completely.
Once the onions and mushroom filling are chilled, assemble the wreath. Roll the pastry out between two pieces of parchment paper to a rectangle about 40x25cm (16×10 in.) in size. Keep the bottom piece of parchment paper under the pastry while filling.
Add the caramelised onions to the centre of the rectangle, then top with the cooled mushroom filling.
Take the edge of pastry closest to you and fold it over the filling, gently pressing with your fingertips to move the pastry under the filling to form a log. Tighten the log as possible but don’t pull or stretch the pastry. Tuck any filling that’s fallen out back in on the sides.
Continue to roll the log over to take up the remaining pastry. Use a water dampened pastry brush to brush along the inner edge of where the pastry folds over for a good seal.
Gently move the log into a circular shape, bringing the two unsealed ends together. Tuck one inside the other and brush with a little water to seal again.
Use the parchment paper under the pastry to slide it carefully onto a large baking sheet.
With a sharp knife, cut about nine slits in the top of the wreath. This allows steam to escape and will give a nice guide to cut the pastry after baking. Avoid cutting where the seams meet at the circle.
Preheat the oven to 200C (400F) again. Chill the pastry if possible while the oven preheats*.
Bake the pastry for 35-40 minutes, or the pastry is a deep golden colour and feels crisp. Cool for about ten minutes before slicing and serving.
Leftovers can be refrigerated in a sealed container for a day or two, and are not too bad if reheated in a hot oven, but this is best fresh.
* Optionally, brush the top and sides of the wreath with an egg wash before baking (skip this step if vegan). This will result in a very golden, crispy outer crust.** Sweet paprika can be subbed here, or leave it out.