Softly whipped cream, vanilla ice cream
Preheat the oven to 350°F (180°C). For the toffee sauce, put all of its ingredients into a saucepan over a medium heat and boil for 2–3 minutes, stirring regularly until smooth. Set aside.
Next, to make the crumble topping, place the flour and lemon zest in a bowl and rub in the butter, leaving it a little rough and uneven. Stir in the sugar and ground almonds. Place the crumble in the fridge until you are ready to use it.
For the filling, melt the 4 tablespoons butter in a wide saucepan or frying pan, add the chopped apples and heat for a few minutes until they start to soften. Add 1/2 cup of the toffee sauce (about half; keep the rest for serving) and continue to simmer for a few minutes longer, until the apples are just cooked.
Pour the filling into two 9-inch pie dishes. Sprinkle the crumble over the top and place in the preheated oven for 20–30 minutes, or until the crumble is a light golden color and the toffee sauce juices bubble up the sides.
Serve warm with softly whipped cream or vanilla ice cream and a jug of the remaining warm toffee sauce