In a medium bowl, combine six tbsps sugar, all-purpose flour, oats, brown sugar, walnuts, lemon zest, 1/4 tsp vanilla, 1/4 tsp kosher salt and cinnamon. Using your fingers, work butter into the flour mixture until crumbly. Transfer the topping into the freezer to let chill for 30 minutes.
In a large bowl, stir together remaining 1/2 cup sugar, 1/4 tsp salt, lemon juice and remaining 1/2 tsp vanilla, along with blueberries, cornstarch and brandy.
Mound some of the crisp topping over each ramekin. Bake in a 350 degree oven until the berries are bubbly and the topping is browned; about 30 minutes.
Serve warm or room temperature with vanilla ice cream.