Preheat the oven to 180°C, fan 160°C, gas 4.
Place the apples, pears and ginger in a small pan. Cover and cook on a medium heat for 5 minutes, stirring occasionally until softened.
Place the mixture in a large, shallow ovenproof dish and top with 75g of the chocolate.
For the crumble topping, mix the oats, caster sugar, butter, flour and vanilla extract together, rubbing the butter between your fingertips until the mixture has a crumbly texture – or you can use a food processor.
Sprinkle the crumble topping over the mixture and bake for 25-30 minutes until golden brown. Melt the remaining chocolate in a bowl set over a pan of simmering water, drizzle over the crumble and serve.