Homity pie with sour-cream pastry and cavolo nero from Prue: My All-time Favourite Recipes by Prue Leith

Ingredients

• 3 tbsp olive oil
• 150 g cavolo nero, roughly chopped
• 350 g floury potatoes, peeled and sliced
• 1 medium egg, beaten
• 90 ml soured cream
• 150 g butter, diced
• a tiny pinch of salt
• 175 g plain flour
• salt and pepper to season
• 125 ml (double) cream
• a small handful of parsley leaves, chopped
• 100 g mature Cheddar cheese, finely grated
• 1 onion, finely chopped
• 400 g leeks (roughly 2 large), finely chopped
• 2 garlic cloves, finely chopped
• a pinch of mustard powder