Impressive vegan mushroom and beetroot wellington

Ingredients

• 4 medium (650g) raw beetroot
• 30g dried porcini mushrooms
• 2 tbsp rapeseed oil
• 2 shallots, finely chopped
• 500g Portobello mushrooms, very finely chopped
• 250g Chestnut mushrooms, very finely chopped
• 3 garlic cloves, crushed
• 2 tbsp Steenbergs organic mediterranean herby rub
• 150g cashew nuts
• 150ml vegetable stock (check if it is vegan if serving to vegans)
• 500g block puff pastry (make sure not to use all butter if serving to vegans)
• 2 tsp Steenbergs nigella seeds
• 2 tbsp oat or other non dairy milk, to glaze