Heat the butter and olive oil in a pan. Add the onion and cook until soft.
Add the mushrooms and garlic. Cook over medium-high heat until all the excess moisture has cooked away.
Stir through the walnuts, breadcrumbs, thyme, Dijon mustard and soy sauce. Season well. Allow the mixture to cool completely.
Heat oven to 200°C. Place the pastry on a lined baking tray. Spoon the mushroom mixture down the centre, leaving a border.
Fold the pastry over the filling and seal the edges. Place seam-side down. Brush with beaten egg and score the top lightly with a knife.
Bake for 35–40 minutes, until puffed and deeply golden. Rest for 10 minutes before slicing.
Heat the butter and olive oil in a pan. Add the onion and cook until soft.
Add the mushrooms and garlic. Cook over medium-high heat until all the excess moisture has cooked away.
Stir through the walnuts, breadcrumbs, thyme, Dijon mustard and soy sauce. Season well. Allow the mixture to cool completely.
Heat oven to 200°C. Place the pastry on a lined baking tray. Spoon the mushroom mixture down the centre, leaving a border.
Fold the pastry over the filling and seal the edges. Place seam-side down. Brush with beaten egg and score the top lightly with a knife.
Bake for 35–40 minutes, until puffed and deeply golden. Rest for 10 minutes before slicing.