Preheat the oven to 200°C/400°F/gas mark 6.
Heat the olive oil in a medium saucepan and add the chopped leek, carrots, green beans and celery, and sauté for 2 minutes.
Stir in the dried herbs, chili flakes, kidney beans and lentils.
Pour over the stock and stir in the slurred corn starch, followed by the Worcestershire, tamari and rosemary sprig.
Bring to a gentle simmer for around 10 minutes. Allow to cool slightly. Discard the rosemary sprig.
For the mashed potato, peel and cut the potatoes into even pieces, so they cook for the same time. Put in a large pan and cover with water. Add one pinch of salt. Bring to the boil, then reduce heat to a simmer. Cook until they are fork tender, around 10-12 minutes, depending on size.
Drain the potatoes in a colander, then return back to the saucepan. Mash really well.
Drizzle in the extra virgin olive oil and mustard, the other pinch of sea salt and black pepper. Stir in the unsweetened plant-based milk and use a fork to mix and fluff it up, getting rid of any lumps at the same time. Finally, stir through the parsley.
Spoon the bean mix into a large baking dish, approx. 12 x 8”. Spoon the mash on top and use a fork to even it out.
Bake in the oven for 20-25 minutes, until golden brown and crisp on top and bubbling.