13min · 8 servings Cookies base • ½ cup butter • ⅓ cup granulated sugar • ¼ cup brown sugar • 1 large egg • 1 teaspoon vanilla extract • 1 & ½ cup all-purpose flour • 1 tablespoon corn starch • ¼ teaspoon baking powder • ½ teaspoon baking soda • ¼ teaspoon salt • ½ cup fresh blueberries washed and dried well. • 1- 1.5 tablespoon blueberry jam Streusel • 3 tablespoon butter softened • 2 tablespoons brown sugar • 2 tablespoons granulated sugar • ⅓ cup flour • a pinch salt • a pinch cinnamon