Start by browning the butter. Place the butter in a small saucepan and set over a medium heat. Once the butter has melted, keep cooking, swirling every now and then, until the milk solids turn a reddish brown and start to smell fragrant. This should take around 5-10 minutes. Remove from the heat and pour into a small heatproof bowl. Leave to cool until the butter has re-solidified. (You can speed this process up by placing the bowl into the freezer for about 10 minutes).
100 g unsalted butter
Preheat oven to 180°C (350°F).
Place the flour, oats and ground almonds in a large bowl and mix together. Dice the browned butter and add this to the dry ingredients. Rub the butter into the dry ingredients until it's the size of peas.
110 g spelt flour, 50 g rolled oats, 25 g ground almonds
Stir the sugars, cinnamon and nutmeg into the flour, salt, oat and butter mixture. Set aside.
50 g light brown sugar, 25 g dark brown sugar, ½ teaspoon ground cinnamon, ¼ teaspoon freshly ground nutmeg, pinch of salt
Remove the stones from the plums and chop each half into 4. Place into a bowl with the blackberries and sprinkle with the sugar and flour. Mix briefly.
450 g plums, 150 g blackberries, 3 tablespoons light brown sugar, 2 teaspoons spelt flour
Divide the fruit between 6 small pie dishes or one regular size pie dish. Sprinkle the crumble mixture evenly over the top and lightly press down.
Bake for 25 minutes or until the crisp topping is golden brown and the fruit has bubbled up around the edges.
Serve warm with plenty of vanilla ice cream.