Preheat oven to 400°. Place sweet potatoes on a large baking sheet and poke all over with a fork. Roast until tender, 50 minutes. Let cool completely.
Scoop out flesh and transfer to a food processor along with cinnamon, brown sugar, vanilla, and salt. Add egg whites and continue to process until combined.
In a large bowl, mix all crumble ingredients until well combined.
Butter two small ramekins. Divide batter evenly and smooth tops. Sprinkle each with crumble topping. Bake until puffy and completely set, 38 to 40 minutes. Serve immediately.
