Rhubarb & Custard Crumble

Ingredients

• 2 tbsp cornflour
• 80 g caster sugar
• 700 g rhubarb, trimmed and cut into 3cm pieces
• 1 tsp vanilla extract
• 180 g plain flour
• 60 g rolled oats
• 80 g demerara sugar
• 100 g cold unsalted butter, cubed
• 500 ml ready-made fresh custard, to serve

Method

1. Heat the oven to 190°C fan. Tip the rhubarb into a large baking dish with the caster sugar, vanilla and cornflour. Toss until every piece is glossy and coated — the cornflour needs to cling to wet fruit so it can thicken those pink juices into syrup rather than puddle. Spread into an even layer.
2. Make the crumble: rub the cold cubed butter into the flour with your fingertips, lifting and letting it fall, until the mixture looks like coarse breadcrumbs with a few larger flecks of butter still visible — those flecks are what melt into buttery pockets in the oven. Stir through the demerara sugar, oats and a generous pinch of salt. Taste a little of the dry mix on your fingertip — it should taste sweet but not flat; the salt is what makes the sugar sing.
3. Scatter the crumble loosely over the rhubarb in craggy clumps — don't press it down. The peaks and gaps are what crisp up into golden, nubbly bits; a flat layer steams instead of crisping.
4. Bake for 35–40 minutes, until the top is deeply golden and you can see thick pink rhubarb juices bubbling up around the edges. If the top is browning before the fruit bubbles, drop the oven 10°C — you want both happening together.
5. Rest for 5 minutes so the filling thickens and stops scalding. Taste a corner of the fruit — if the rhubarb has gone shy, a tiny extra pinch of salt across the top wakes it back up. Spoon the crumble into bowls, pour over plenty of warm custard at the table, and let it pool into every craggy gap.