For best results use the Breville Scraper Mixer™

Preheat oven to 200°C

Assemble the mixer with the scraper paddle. Add flour, sugar and almond meal and butter into mixer bowl. Slowly turn mixer to KNEAD/FOLD setting and mix until it resembles sand like texture; add egg yolk and water (if needed) and mix until pastry combines

Remove pastry from bowl onto a clean surface and shape into a flat disc. Cover pastry with plastic wrap and refrigerate for 30-40 minutes

Meanwhile process sugar, almonds, cinnamon, oats and butter in a food processor. And pulse mixture until roughly combined. Set mixture aside

Toss rhubarb in white sugar set aside

Roll pastry out to a 35cm circle between two sheets of baking paper. Remove top sheet of paper and slide pastry onto a baking tray. Place half of the crumble into middle of circle. Top with apples then rhubarb. Sprinkle with remaining crumble. Bring edges up around filling leaving top open. Brush pasty lightly with egg white and sprinkle with raw sugar

Bake in oven for 30-45 minutes or until golden

Serve warm with custard or ice cream