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).
Preheat oven to 180°C (350°F).
Place the flour, ground almonds and oats 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.
Stir the pecans, sugar and cinnamon and salt into the flour, oat and butter mixture. Set aside.
Place the blueberries into a bowl and sprinkle with the sugar, orange zest, orange juice, vanilla extract and cornflour. Mix briefly.
Divide the fruit and juices between 4 small pie dishes or one regular sized (9”) 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 or Greek yoghurt.