2) For the topping, place the remaining flour and caster sugar, the brown sugar and the salt in the bowl of a food processor fitted with a steel blade and pulse a few times to combine. Add the butter and pulse until the butter is pea-sized.
3) Pour the mixture into a bowl, add the oats, and work it with your hands until it resembles breadcrumbs. Add the 60g of almonds and mix well. Spread the topping evenly over the plums, making sure the fruit is covered. Sprinkle with some extra almonds.
4) Bake for 40 minutes, or until the fruit is tender and bubbly and the topping is golden brown. Serve warm or at room temperature.