Preheat the oven to 200°C, 400°F, Gas Mark 6. Roll out the pastry on a floured surface to fit a 30cm (12 inch) flan tin. Prick all over with a fork then bake blind for 10-15 minutes.
Remove the beans and bake for a further 5 minutes. Turn the oven down to 180°C, 350°F, Gas Mark 4.
Mix 175ml (6fl.oz) condensed milk with the muscovado sugar to make the toffee then set aside.
To prepare the apples, peel, halve and remove the core of each and sprinkle with lemon juice to prevent discolouration.
Next make the sponge mixture by whisking the remaining condensed milk with the remaining ingredients, using an electric hand whisk.
Once the pastry case is cooked, spread the toffee mixture over the pastry base.
Slice the apple halves into thin slices and arrange in the pastry case (keep the slices in the shape of the apple half then transfer to the pastry case and flatten slightly to create a fanned effect from the centre to edge of the pastry, repeat until all the apples are used.
Spread the sponge mixture between the apples then, bake in the oven for 40-50 minutes until the sponge is well-risen and golden brown.