Preheat the oven to Gas Mark 7, 220°C, fan 200°C. Put the pears into a 1.4 litre (2½ pints) shallow ovenproof dish. Scatter over the blackberries and half of the fudge.
For the topping, put the cold butter and flour into a food processor and pulse until it resembles crumbs. Tip into
a bowl and add the rest of the fudge, sugar (reserving 1 tablespoon), the oats and the hazelnuts; mix together.
Scatter the topping over the pear mix, then sprinkle with the reserved sugar and bake for 20-25 minutes or until
the topping is golden brown. Serve warm with vanilla ice cream or hot custard.