• Preheat the oven to 200C/180C fan/gas 6 and line a large baking tray with tin foil.
• Spread the mushrooms onto the lined tray, drizzle with 1 tbsp of the olive oil, season lightly and roast in the oven for 15 minutes. Remove and set aside, reserving any juices (switch the oven off).
• Meanwhile, heat 2 tbsp of the olive oil in a large frying pan over a medium heat. Add the onions and garlic and cook for 10 minutes, stirring occasionally, until softened.
• Reduce the heat to medium low, add the chopped rosemary and thyme leaves and sugar. Cook for 10 minutes, until the onions are golden.
• Pour in the Guinness and bring to a simmer. Cook for 10 minutes so that the liquid reduces.
• Reduce the heat to low and add the mushrooms and any juices. Add the flour, mustard and soy sauce, stir well to combine and simmer gently for 15 to 20 minutes, stirring regularly. After 10 minutes, heat the oven again to 200C/180C fan/gas 6. Taste and adjust the seasoning, adding more salt, pepper, mustard or soy sauce, if you like.

Assemble and bake:

• Spoon the mushroom mixture into a deep pie dish (approx. 22cm to 26cm diameter) and leave to cool for around 10 minutes.
• Remove the puff pastry from its packaging and unroll it. If you need to, roll it a little thinner until it’s big enough to cover the pie dish. Brush the rim of the dish with water and lay the pastry over the top. Cut off the excess pastry and crimp the edges either by pinching it between your finger and thumb all the way round, or by pressing it against the dish with the back of a fork. I like to make leaves to decorate the top of the pie using the excess pastry!
• Brush the remaining tbsp of olive oil over the pastry (keep some back to brush any decoration you make for the top of the pie).
• Use a small sharp knife to cut a little cross in the centre of the pastry so that steam can escape.
• Bake in the oven for 30 to 35 minutes, until the pastry is golden brown. Remove and serve hot with your choice of vegetable side dishes.