Preheat the oven to 350 degrees. Grease a 9 inch square or 11 x 7 inch rectangular baking pan.
Chop the apples into bite size pieces. In a large bowl, toss together the apples, blueberries, brown sugar, cornstarch, cinnamon, cardamom, lemon juice, salt, and vanilla. Spread it evenly across the prepared pan.
In another bowl, stir together the flour, brown sugar, oats, pecans, and salt. Pour the melted butter over top and stir until all the dry ingredients are moistened.
Use your fingers to pinch together the crumble to form various sized crumbles. Sprinkle them evenly over the fruit filling.
Place the crumble in the oven and bake for 45-55 minutes, or until the apples are fork tender. Check the crumble at 40 minutes. If the crumble is already well browned, loosely cover it with foil for the remaining bake time. Serve the crumble warm with ice cream, if desired.