Prepare the Blueberry Filling: In a large bowl, gently combine the blueberries, granulated sugar, all-purpose flour, lemon juice, and lemon zest (if using). Make sure the blueberries are coated evenly. This mixture will create a sweet and slightly thickened base for your crumbles.

Make the Crumble Topping: In a separate bowl, whisk together the all-purpose flour, brown sugar, cinnamon, and salt. Add the cold, cubed butter to the dry ingredients.

Cut in the Butter: Using a pastry blender or your fingertips, cut the butter into the flour mixture until it resembles coarse crumbs. It's important to keep the butter cold for a crumbly texture. You can also use a food processor for this step, pulsing until the mixture comes together in small clumps.

Assemble the Crumbles: Preheat your oven to 375°F (190°C). Divide the blueberry filling evenly among six ramekins.

Top with Crumble: Sprinkle the crumble topping evenly over the blueberry filling in each ramekin, ensuring the fruit is well covered.

Bake the Crumbles: Place the ramekins on a baking sheet and bake for 25-30 minutes, or until the topping is golden brown and the blueberry filling is bubbling. The baking sheet helps to catch any drips.

Cool and Serve: Remove the Mini Blueberry Crumbles in Ramekins from the oven and let them cool for at least 10-15 minutes before serving. This allows the filling to thicken slightly.