Preheat the oven to 180˚C.
In a saucepan, melt 25g of butter with 25g brown sugar until bubbly and starting to caramelise. Add the chopped apple pieces and mincemeat and stir once to coat in the caramelised mixture.
Cook for a further 2 minutes to colour and slightly soften the fruits. Remove from the heat and transfer in a oven dish.
Then, In a bowl, combine the flour, baking powder, porridge oats, caster sugar and mixed seeds. Rub in the rest of the butter (75g) until soft and crumbly. Scatter the mixture over the fruits.
Bake in the oven 35-45 minutes until golden brown and cooked through.
Remove from the oven and serve warm with a dollop of whipped cream.