Cooked this yesterday to share with a friend; mentioned it to another friend and had to promise to share the recipe, so here it is.
I cooked mine in my Dutch oven, so it could go straight from the hob to the oven, but you could start the filling off in a good size saucepan and then transfer it to a casserole dish to bake.
For the filling
1-2 tablespoons sunflower oil
2 smallish or 1 large onion, roughly chopped
2 cloves garlic, crushed
150g chestnut mushrooms, quartered (or cut into six segments if large)
2 large sweet potatoes, cut into 1″ cubes
2 teaspoons caraway seeds
500ml veg’ stock
400g tin chickpeas, drained
For the topping
250g barley flour
50g porridge oats
Optional – A couple of handfuls of grated cheese (I used goats’ Gouda)
Heat over to 200ºC
While the oven is coming to temperature, heat the oil over a low to medium heat and sweat the onions and garlic until softened, stirring regularly.
Add the mushrooms and cook for about five minutes, until softening.
Add the sweet potatoes, caraway seeds, and stock; stir well and bring to the boil. Then simmer uncovered for 15 to 20 minutes.
Meanwhile combine the topping ingredients and work between your fingertips until the mixture resembles coarse breadcrumbs.
Stir the chickpeas into the filling.
Drain of any excess liquid (I think I poured about 2 tablespoons away).
Add the crumble topping and bake for around 30 minutes.
If topping with cheese sprinkle it over the top about 5 minutes before the end of the cooking time.
Easy to do a vegan version by replacing the butter with dairy free spread (I like Suma Sunflower Spread for baking) and skipping the cheese.
For a gluten free version I would probably use buckwheat flour.