Mushroom spinach potato pie

Name: Mushroom, spinach & potato pie
Ingredients: 400g baby spinach; 1 tbsp olive oil; 500g mushroom, such as chestnut, shiitake and button; 2 garlic clove, 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