Preheat the oven to 375 degrees.
In a medium mixing bowl, stir together the blackberries, granulated white sugar and half the flour (⅛ cup).
For the topping: In a separate bowl, stir together the other half of the flour, walnuts, oats, cinnamon and brown sugar.
Use your hands to work in 2 tablespoons of butter into the topping mixture. Keep squeezing the chunks of butter into the toppings mixture until well-combined and topping will resemble large crumb-y chunks.
Place five small (4 ounce) ramekins on a baking sheet and spray with cooking spray.
Spoon the blackberry mixture evenly into the five ramekins.
Top each ramekin with some of the topping.
Bake at 375 for about 25 minutes.
