Dice the onion and mince the garlic. Chop the mushrooms, keep them chunky as they reduce down quite a lot so only chop them in half or quarters. Don't worry, they will cook through!

Heat up the oil and gently fry the onion and garlic until the onion is translucent. Add the mushrooms. Try to use a big, wide pan here to give them lots of space to cook. Fry off the mushrooms on a low heat until they soften.

Add the beer, soy sauce and balsamic vinegar. Add the bullion powder and let reduce a little bit. Here you might need to add some more water or a little flour to thin or thicken up the sauce. Mince up the fresh thyme and rosemary and add to the mushrooms. You are aiming for the mushrooms to become quite sticky but not too dry. Once reduced season how you would like with the salt and pepper. It doesn't matter if the mushrooms aren't fully cooked through, as they will cook more in the oven.

Pre-heat the oven to gas mark six. Grease or line your chosen pie dish. I decided not to blind bake my pastry, as it shrinks in the oven and can be difficult to handle afterwards. Line the pie dish with the pastry. I used a little beaten egg to bind the pastry together. Otherwise use a fork to press the pastry together. To make adding a top to the pie easier I recommend making your pastry a bit longer than necessary (so it hangs over the pie dis, so there is some overlap over the top of the pie.

Add the grated cheese into the mushrooms and mix through. Spoon the mushroom mixture into the pastry case and press down to flatten it. Top the pie with pastry. Fold the overhang over the top of the pie to seal it. Either bind with egg or use a fork again. You can use the leftover pastry for decorations, otherwise save it for another meal. Brush the pie with egg (again optional if you want a vegan version). Bake in the oven for 40-50 minutes, until golden.