1. Preheat your oven to 200°C/Fan 180°C/Gas 6. Peel the potatoes and chop them into 2cm-thick cubes. Tumble them into a large pan, add a pinch of salt and cover with cold water. Place on a medium-high heat and bring up to a boil then simmer for 10-15 mins, till the potatoes are tender when pierced with a sharp knife. Drain and leave to steam dry in the colander for a couple of mins.
2. While the potatoes simmer, peel and finely chop the onion. Peel and grate or crush the garlic cloves. Trim the leeks and wash out any grit. Finely slice them.
3. Tip the potatoes into a bowl or the pan. Add 100ml of the soya cream, 2 tbsp vegan butter and 2 tbsp wholegrain mustard. Add a generous pinch of salt and pepper. Mash till smooth and creamy, adding an extra 1 or 2 tbsp of the butter alternative or a splash of milk alternative, if necessary. Set aside.
4. Place a large, deep frying pan on a medium heat and add 2 tbsp olive oil. Add the onion and cook gently for 5-6 mins till starting to soften. Add the garlic and leeks to the pan and fry for 5 mins, stirring often, till the leeks have softened.
5. Meanwhile, drain the banana blossom and chop into 2cm-thick chunks. Drain and rinse the butter beans. Roughly tear the mushrooms into small pieces, keeping any smaller ones whole.
6. When the leeks have cooked for 5 mins, drop in the mushrooms and cook, stirring, for 3-4 mins till they have softened slightly.
7. Pour the white wine into the pan and let it bubble for 1 min. Then pour in the remaining soya cream and season with a good pinch of salt and pepper. Gently bring up to a simmer. Add the banana blossom and butter beans to the pan and simmer on a low heat for 5 mins.
8. Finely chop the dill and parsley, discarding any thick stalks. Rinse the capers and squeeze dry.
9. Add the fischy sauce and a pinch of smoked paprika (if using) to the pan. Finely grate in the zest from 1 lemon and squeeze in the juice from half. Sprinkle in the herbs and capers and gently stir. Taste and add more salt, pepper or lemon juice, if you think it needs it.
10. Spoon the filling mix into a medium-sized ovenproof dish. Top with the mash. Slide into the oven for 30 mins, till the top is golden and the filling is bubbling. Serve with lemon wedges and peas on the side.
11. Taste of the Sea
For an extra splash of seaside flavour, add 2 tbsp of dried sea salad to the sauce in step 9. The seaweed gives the pie a deliciously briny flavour. However, the sea salad may contain traces of crustaceans, fish and molluscs, so the dish will no longer be vegetarian.