Heat the oil in a frying pan and fry the mushrooms for about 5 minutes then set aside.
Roughly chop the haggis (I also bashed it about in the frying pan) and fry for about 5 minutes and remove from the heat.
Steam the cabbage for about 5 minutes.
If the pastry isn't ready-rolled, roll it out on to a lightly floured surface into a rectangle about the depth of a pound coin (don't worry if the rectangle isn't even, you can make it look neater when you're folding it up).
Cut the pastry in half and layer the mushrooms on half of each half, leaving a border.
Put the haggis on top of the mushrooms and slightly flatten with your hand.
Put the cabbage on top of the haggis.
Using your finger, wet the edges of the pastry with some of the soya milk.
Fold over the empty half of the pastry over the haggis, mushroom and cabbage filling and crimp down the edges with your fingers.
Glaze the pasties with the soya milk and score two slits in the top of each one.
Line a baking tray with baking paper and bake in the oven at 180C for about 20 minutes, until golden.
Recipe by Planet Veggie at https://www.planetveggie.co.uk/vegan-haggis-mushroom-cabbage-pasties/