Preheat the oven to 180°C, fan 160°C, gas mark 4 and lightly grease a 1-litre shallow ovenproof dish.
Fill with the blackberries and conference pears. Sprinkle with lemon juice and 20g of the light brown sugar, then set aside.
Place the plain flour and the unsalted butter in a bowl and rub together until the mixture resembles breadcrumbs. Stir in the remaining 30g of light brown sugar, the porridge oats and the fruit, nut and seed mix.
Sprinkle over the fruit and press down lightly. Cook in the preheated oven for 35-40 minutes until the topping is golden and the pears are tender.
Allow to stand for 10 minutes, then serve with Taste the Difference clotted cream for a crunchy, seasonal dessert.
Cook's tip: You could use a mix of your favourite dried fruits and nuts in the crumble topping, or try with apples in place of the pears.