oooh tablet, lovely and I'm scottish so know all about its arteryblocking deliciousness from my childhood!! But the tin I have is the already caramelised stuff iykwim not the normal condensed milk which you need to make tablet.
Put unopened tins of condensed milk in a large casserole dish, cover with water and bring to the boil over a high heat. Preheat oven to 140c/Gas 1. Cover casserole with a lid and place in the oven for 3 and a half hours. Cooking the tins this way ensures they don't boil dry. Set aside to cool overnight.
To make base, whizz biscuits in food proessor to fine crumb. Transfer to mixing bowl add butter and cinnamon and stir. Press mix into 25cm loose bottomed tart tin and place in fridge.
Peel and core apples, cut each one into 8. Melt butter in pan over low heat. Add apples and sugar and cook until golden brwon and just softening but keeping their shape. Stir in lemon zest and juice.
Open tins of cold boiled condensed milk and spoon toffee mixture onto the biscuit base ( use a warm spoon that you keep dipping in a mug of hot water to prevent sticking ). Arrange apples evenly over the top.
Whisk the cream in a large bowl until just thick, then spread over the apples. Keep in the fridge until needed, then remove tart from tin and sprinkle almonds on just before eating.