For the pastry, place the butter, lard, flour and salt into a food processor. Pulse the mixture until it resembles coarse breadcrumbs.
Place the pastry into a mixing bowl and, using a round-bladed knife, stir in enough water to bind the mixture together. Lightly knead the dough until well amalgamated, dust with flour and slip into a plastic bag. Chill in the fridge for 30 minutes before using.
Preheat the oven to 180C/350F/Gas 4 and warm a baking sheet.
Roll out the pastry as thinly as possible. Line a 20cm/8in wide by 4cm/1½in deep tart tin and lightly prick the base of the pastry with a fork all over. Place onto a baking tray, line with greased aluminium foil and baking beans and bake blind for 15-20 minutes.
Remove the baking beans and foil. Place the tart case back into the oven and cook for a further 10 minutes, or until it is pale golden, crisp and cooked through.
Fry the bacon in a dry, non-stick frying pan for 1-2 minutes, or until crisp. Drain onto kitchen paper and spread out evenly over the base of the cooked tart case.
Whisk the egg yolks and whole eggs together in a bowl. Stir in the cream and season with salt, pepper and nutmeg. Pour the mixture into the pastry case and cook for 30-40 minutes, or until nicely puffed and the surface of the custard is pale golden and just set.
Eat warm, or at room temperature.