Leek, cheese & potato pie

Name: Leek, cheese & potato pie
Prep time: 35 min
Cook time: 1 h 10 min
Total time: 1 h 45 min
Cuisine: European, British
Ingredients: 500g (2 large) waxy potatoes; 1 tbsp olive oil; 1 bay leaf; 1 tbsp butter; 2 leeks , halved and cut into ½ cm thick slices; 1 onion , chopped; grating of nutmeg; 1 tsp Dijon mustard; 1 tsp wholegrain mustard; 20g parmesan or vegetarian alternative, grated; 20g mature cheddar; 250g melting cheese , like doux de montagne, ogleshield, or reblochon, sliced (use vegetarian if needed); 250g plain flour , plus extra for dusting; 140g cold butter , plus extra for the dish; 2 tsp vodka; 2-4 tbsp iced water; 1 egg , beaten, to glaze