Preheat oven to 350 degrees F (180 degrees C).
Finely chop the Walnut (1/2 cup). Peel, core, and dice the Apple (3). Juice, and zest the Lemon (1). In a small bowl, combine Water (1 tablespoon) and Corn Starch (1 teaspoon) to make a slurry.
Grease a 9-inch square baking pan.
In a food processor, pulse together the All-Purpose Flour (2 cup), Brown Sugar (1/2 cup) and Salt (1/2 teaspoon). Add the Unsalted Butter (12 tablespoon) and pulse until the mixture comes together into a ball.
Press dough into bottom of a prepared baking dish. Bake until crust is pale golden, 25 to 30 minutes. Let cool.
Heat a saucepan over medium heat. Add the diced apples, Dried Cranberries (1/2 cup), Granulated Sugar (1/4 cup), lemon juice and zest, and Water (1/2 cup). Cook until apples are softened and cranberries are plump 8-10 minutes.
Bring mixture to a low boil, and stir in the cornstarch slurry. Cook for another minute until thickened. Remove from heat, and let cool.
To make the streusel, in a small bowl, whisk together the Granola (1/2 cup), Brown Sugar (1/4 cup), All-Purpose Flour (1/4 cup), Ground Cinnamon (1/2 teaspoon), Whole Nutmeg (1/2 teaspoon), and Fine Sea Salt (1/4 teaspoon) in a small bowl.
Add the Unsalted Butter (4 tablespoon) and work it into the flour mixture with your fingertips, forming pea-sized crumbs.
Spread apple mixture over the shortbread.
Sprinkle streusel over the apples. Bake 20 minutes, until topping is golden.
Allow to cool before cutting into bars. Enjoy!