Line a tray with baking parchment and grease with oil.
Boil 125ml water with brown sugar, then stir in cream of tartar, syrup, and treacle.
Cook toffee mixture to 140°C, pour onto the tray, and cool.
Preheat the oven to 150°C.
Cream butter and sugar, then mix in egg yolk and flour.
Chill wrapped pastry in the fridge for one hour.
Roll pastry to 5mm thickness and line a 20cm tart ring.
Fill pastry with baking weights and chill for another hour.
Blind bake for 35 minutes, remove weights, and bake for 10 more minutes.
Melt butter, sugar, and orange zest in a pan.
Add Bramley apples and cinnamon, cooking until pureed.
Stir in eating apples for 2 minutes and remove the cinnamon stick.
Drain excess liquid from apples and let cool.
Preheat the oven to 180°C.
Rub crumble ingredients together with fingertips until combined.
Bake crumble on a tray for 20 minutes, stirring every five minutes.
Fill the pastry case with apples and top with toffee chunks and crumble.
Bake at 180°C for 12 minutes until bubbling.
Serve warm with custard or cream.