1. Preheat the oven to 180°C (350°F).
2. In a bowl, mix the berries, sugar, cornstarch, and lemon juice. Spread evenly in a baking dish (20 x 20 cm / 8 x 8 in).
3. In a mixing bowl, combine the oat pulp, oats, almond flour, sugar, cinnamon, and salt.
4. Stir in the melted coconut oil until the mixture is crumbly and holds when pressed.
5. Scatter evenly over the berries.
6. Bake for 25–30 minutes, until the topping is golden and the fruit is bubbling.
7. While the crumble bakes, whisk the cornstarch with a little oat milk to make a smooth slurry.
8. In a saucepan, heat oat milk, sugar, and vanilla. Slowly whisk in the slurry.
9. Cook over medium heat until thickened (5 – 7 minutes), whisking constantly.
10. Spoon the warm raspberry crumble into bowls and pour over the vegan custard.