Vegan squash and mushroom pie

Name: Vegan squash and mushroom pie
Ingredients: 1kg/2lb 4oz Maris piper potatoes, peeled and diced; 2 tbsp olive oil; 1 red onion, finely chopped; 3 garlic cloves, crushed; 2 celery sticks, finely chopped; 1 tbsp cumin seeds; 1 tbsp sweet smoked paprika; 1 red chilli, finely chopped; 2 bay leaves; 1 stick rosemary; 350g/12oz chestnut mushrooms, quartered; 1 small butternut squash, roughly chopped; 165g/5¾oz pitted dates, roughly chopped; 300g/10½ oz chopped fresh tomatoes; 400g tin chickpeas; 2 preserved lemons, finely chopped; 100g/3½oz vegan butter; 2 tbsp finely chopped fresh mint; vegetable oil, for deep frying; handful parsley leaves