Mushroom, spinach & potato pie

INGREDIENTS

• 400g baby spinach
• 1 tbsp olive oil
• 500g mushrooms , such as chestnut, shiitake and button
• 2 garlic cloves , crushed
• 250ml vegetable stock (made from half a low sodium vegetable stock cube)
• 300g cooked new potatoes , cut into bite-sized pieces
• 1 tbsp grain mustard
• 1 tsp freshly grated nutmeg
• 2 heaped tbsp light crème fraîche
• 3 sheets filo pastry
• 300g each green beans and broccoli, steamed