Tender, juicy, meaty portobello mushroom, stuffed with sweet caramelized onions, a sprinkling of thyme, all topped with buttery, crisp pastry. This is seriously the easiest Vegan Mushroom Pie you will find & it’s soooo good!!! Perfect for making in advance too!
Heat a pan over a medium heat, add the oil (or a few tablespoons of water or broth) and saute the onions until golden brown. It will take around 15 minutes. Towards the end add the optional sugar to make them even more brown, sweet and caramelized.
Remove the onions from the heat and leave to cool completely. If you need to hurry them along, remove them from the pan and spread out in a thin layer on a plate.
Remove the stems from the mushrooms. (To save wasting them you can chop them finely and add them to your gravy). Wipe the mushrooms clean with a dry cloth. DO NOT wash them in water because they will absorb some then steam rather than roast.
Add the flour to a bowl and stir in the salt. Add the vegan butter and either cut or rub it into the flour. I tend to rub it in with the tips of my fingers. When ready the flour will look like coarse breadcrumbs and there will be no lumps big lumps of butter. A few little tiny lumps are fine. (See my video to see how mine looked).
Once the butter is rubbed in add the water a tablespoon at a time until you can form it all into a dough with your hands. It's important to do it gradually. You will probably need 3-4 tablespoons but all flour have different absorbencies so it will vary. The dough should be soft, come together well but not be sticky. If you do accidentally add a little too much water you can add a little more flour if you need to but avoid this if you can. Also only handle it as much as you need to. Over-handling pastry makes it tough.
Lightly flour your surface and roll the dough out. You need to roll it just big enough that both mushrooms can sit on it face down and there be about ½ an inch of pastry all the way around each one.
Once it's at that size cut a circle, using the mushroom as a guide about ½ an inch bigger than each mushroom. (See my video above to watch me do it). The circle doesn't have to be perfect.
Remove the mushrooms and put them on a greased baking sheet top down. Fill their bowl shaped underneaths with the caramelized onions until they are level with the brim then sprinkle with a generous sprinkling of dried thyme and salt and pepper. It is really important that your onions are totally cool.
Top the mushrooms with the pastry circles and use your fingers to pinch it in tight all the way around the edges. You can crimp it if you want it to look extra pretty but it isn't necessary.
At this stage you can store the 'pies' in the fridge for up to 2 days. Just cover them with cling wrap to stop them drying out, then when you want to bake carry on with the next step.
Mix the milk and maple syrup in a small bowl or cup then brush the top of each pie generously with it. Use a sharp knife to make a small incision in the middle of each pastry top.
Place in the preheated oven and bake for around 30 - 35 minutes until the pastry is crisp.
For this recipe, choosing the right shaped portobello mushrooms is key. When turned upside down, they need to not be flat. When you cut the stems out, they need to have space to put the caramelized onions so ones with good depth and almost a shallow bowl shape are necessary. That way you can fill them generously before topping them with the pastry. Watch my video below to see what my mushrooms looked like. These pies can be made ahead of time by up to 2 days. Follow the instructions up to step 10, then cover with cling wrap and refrigerate until needed. Continue with the steps 12 & 13 immediately prior to baking. You will have some pastry offcuts left after making this. My tip for using them up is to roll it out thinnish, and cut circles big enough to line a muffin tin, or just grab pieces and press it into the muffin tin with your fingers if you're lazy like me. Fill ¾ of the way with your jam of choice then bake on 375 for about 15 minutes or until the jam is bubbling and the pastry crisp. My son's favourite! Be sure to wait for the jam to cool down before attempting to eat. It will be scalding hot!