Salmon, leek and potato pie

Ingredients

• 3 large potatoes, cut into chunks
• 30 gram butter, plus 20g extra
• 1 leek, finely sliced
• 1 tablespoon plain flour
• 1 1/2 cup milk
• 400 gram boneless salmon fillet, skin removed, cut in 2cm pieces
• 1 cup firmly packed baby spinach leaves
• 1 tablespoon dill, chopped
• 1 beaten egg
• 1/3 cup parmesan, grated
• 2 tablespoon dried breadcrumbs
• steamed green beans, lemon
• wedges, to serve