Cut the celeriac, parsnip and sweet potato in smallish chunks – 2-3cm square. Steam for 15 minutes (or until tender but not mushy).
Gently saute the red onion and garlic in the oil for 5 minutes. Remove from the heat and crumble in the stock cube. Stir well.
Add the soya yoghurt, 1 teaspoon of miso, nutmeg, herbs and black pepper. Adjust to taste, adding more miso if necessary (soya yoghurt is naturally quite sweet so you may need more miso than you would normally use to balance that out).
Stir the yoghurt mixture in with the steamed vegetables, stirring well so that everything is well coated.
Place the mixture in an ovenproof dish.
To make the crumble, place the porridge oats, wholemeal flour, vegan margarine and salt in a large bowl.
Rub with fingertips until it resembles very course breadcrumbs.
Mix in all of the other crumble ingredients.
Spread the crumble mix on top of the vegetables in the ovenproof dish.
Cook for about 35 minutes until the crumble is golden on top. Check frequently and place a sheet of foil over the top if it's browning too quickly.
Recipe by Veggie Runners at https://www.veggierunners.com/2015/04/10/vegan-savoury-crumble/