Preheat oven to 350 degrees.
Place the rinsed berries/diced fruit into a mixing bowl. Combine the sugar, cornstarch and salt in a small dish and sprinkle over the fruit. Gently stir to combine well. The cornstarch mixture will begin to dissolve and may look “milky” on the fruit. That is perfectly normal.
Divide the fruit into 4 single serve oven-safe dishes. Set these dishes on a baking tray for easy transfer in and out of the oven.
In a small mixing bowl, combine the oats, flour, sugar and cinnamon together with a spoon. Drizzle in the melted butter a little at a time until it is damp, but not dripping with butter. You may need a little more or less than the recipe indicates. Sprinkle the crumble mixture on top of the fruit.
Place the prepared dishes in the preheated oven and bake for 25 minutes. Remove and serve as it is or top with ice cream or whipped cream.