Fill the kettle and boil it. Peel the potatoes. Chop them into smallish chunks. Fill a pan with hot water from the kettle. Add the potatoes. Cover. Bring to the boil. Turn the heat down. Simmer for 20 mins till the potatoes are soft.
Heat your oven to 180°C/Fan 160°C/Gas 4. Warm 1 tbsp olive oil in a deep frying pan or wok. Add half the pack of lardons. Stir and fry for 5-8 mins till the lardons are golden brown. Lift them out of the pan. Pop them on a plate.
Add the pork mince to the pan. Cook over a medium heat for 5-8 mins till the mince is browned. Stir every now and then to break up the lumps and make sure the mince is evenly browned.
While the mince cooks, trim the leek and slice a cross into the top of it so you can open the leek out. Rinse out any grit. Finely slice it. Rinse and pat dry the sage. Finely slice the leaves. Peel the apple. Quarter it. Slice out the core. Slice into wedges.
Lift the mince out of the pan. Add it to the lardons. Add the leeks to the pan. Season with salt and pepper. Stir and fry for 5 mins till the leeks are soft and have a little colour to them. Stir in the cornflour. Cook and stir for 1 min.
Slowly pour in 150ml of the milk. Keep stirring to make a smooth sauce. Add 100ml hot water from the kettle. Add the lardons and mince back into the pan with the sage and apple. Simmer for 5 mins with the lid on. Taste and adjust the seasoning.
Drain the potatoes. Tip back into the pan. Add some salt and pepper. Mash over a low heat till the potatoes are smooth and any excess water has cooked off. Add a splash of milk if you think they need it.
Spoon the pie filling into an ovenproof dish. Top with the mash. Bake for 30 mins till golden and bubbling. While the pie cooks, break the broccoli into florets. Cook in a pan of boiling water for 5 mins till just cooked. Drain. Serve with the pie.