1. Preheat the oven to 350 degrees F. Line an 8 x 8-inch baking dish with parchment. Set aside.

Shortbread Crust

1. In a large bowl, add the melted unsalted butter, sugar, sourdough discard, vanilla extract and salt. Mix with a whisk until smooth. 
   113 grams unsalted butter, melted, 38 grams sugar, 50 grams sourdough discard, 4 grams vanilla extract, 1 gram salt
2. Add the flour and mix with a rubber spatula until a dough forms. 
   175 grams all-purpose flour
3. Pinch off pieces of the dough and scatter them evenly in the prepared baking dish. With your fingers or the back of a measuring cup, press the dough to form a crust. Bake for 15 minutes, then remove from the oven. 

Apple Filling

1. While the shortbread bakes, prepare the apple filling and streusel topping. 
2. Peel and slice the apple into 1/8th inch pieces and add them to a medium bowl. To the apples, add the sugar, flour, cinnamon and nutmeg. Mix with a rubber spatula until the apples are fully coated with the sugar mixture. Set aside.
   300 grams apples, see notes, 38 grams sugar, 27 grams all-purpose flour, 3 grams cinnamon, 1 gram nutmeg

Streusel Topping

1. To a small bowl, add the old-fashioned oats, brown sugar, cinnamon, and salt. Whisk until evenly incorporated. 
   90 grams old-fashioned oats, 75 grams brown sugar, .5 gram cinnamon, 3 grams salt
2. Cube the cold butter and add to the oat mixture. Cut in the butter with a pastry cutter, two forks or even your fingers, until it looks like coarse crumbs. Store in the fridge until ready to use. 
   57 grams unsalted butter, cold

Assemble & Bake

1. Once the shortbread crust is out of the oven, evenly top the apple filling on the warm crust. Then sprinkle the streusel on top. Continue to bake for 35–40 minutes or until the apples are soft and tender. I like to use a toothpick to check.
2. Cool at room temperature for at least 30 minutes before placing in the fridge to chill for at least 2 hours, overnight is best, for easy slicing.
3. Slice into 12-16 even slices; serve cool, room temperature or warm. Top with ice cream, homemade caramel sauce (shared below!) or serve plain. Enjoy!

Homemade Salted Caramel

1. To a medium pot, add white sugar and heat to medium heat on the stovetop. Leave the sugar for a few minutes. Once the sugar starts to melt, continue to give it a stir. Typically, it will dissolve completely in about 8-10 minutes. Keep an eye on it, and be sure the sugar doesn’t burn.
   200 grams sugar
2. Next, once the sugar is melted, add in the room temperature butter, stirring vigorously. It will begin to bubble and rise. Be sure to continue to mix, as it will take some stirring to fully incorporate the sugar and butter.
   85 grams unsalted butter, room temperature
3. When the sugar and butter are combined, slowly pour in the heavy cream while simultaneously stirring, then the salt.
   120 grams heavy cream, room temperature, 3 grams salt
4. Continue to cook until the caramel begins to bubble and rise again, about 1-2 minutes.
5. Remove from the heat and pour into a small bowl to cool.