Place the granola bars in a food processor and process to a coarse crumb consistency.
In a large mixing bowl, add the granola bar crumbs, flour, brown sugar and melted butter and stir to mix.
Spread the mixture onto a pan lined with parchment paper and bake in a preheated 350º oven for 20 minutes, stirring occasionally. Let cool completely.
Spead half of the crumb mixture onto the bottom of an 8x8" baking dish. Reserve the other half of the crumbs.
In a large mixing bowl, add the softened ice cream and stir in the lemon extract. Stir in the frozen blueberries. Pour the mixture over the crumbs in the 8x8" baking dish. Sprinkle the remaining crumbs over the top, cover with aluminum foil and freeze for at least 3 hours.
Let the dessert sit for about 5 minutes after removing from the freezer to soften. Then cut into squares and serve.