Blend all crust ingredients EXCEPT FOR EGG YOLKS until they are the texture of coarse meal. (You can use a fork, a pastry blender or a food processor). Add egg yolks and mix well to blend. **Set aside 1/4 of this mixture and save for later**. Using the remaining 3/4 of the crumbs, firmly pat them down over the bottom and up the sides of a tart pan with removable bottom disk or a large pie pan. Make sure crust is firmly pressed down into the pan and the sides to form a solid crust.
Peel, core, and cut the apples into thin slices. Place sliced apples in a large bowl. Add 1/4 cup brown sugar, 1 TBSP flour and 1/2 tsp. cinnamon. Mix well to coat apple slices.
Once apples and dry ingredients are mixed together, gently "pour" or spoon apples onto crust. Position apples so they mound in the center and fill in the crust.
Sprinkle reserved 1/4 of the crust mixture over the top. I find it helpful to hold one hand up around the edge of the pan to try and catch the crumbles before they fall off the tart. Just scoop up any crumbles that fall onto your work surface and put them back on that tart! Cover the entire top of the tart.
Bake at 400 degrees for 15 minutes, then reduce heat to 350 degrees and bake until the top begins to turn golden brown (approx. 25-30 minutes). Keep an eye on it and remove tart when golden brown. Let cool just a bit. If using a tart pan, hold your hand on the bottom of the tart and gently press upward on the metal disk to release the tart from the pan. Place the tart (keeping disk on the bottom of tart) on serving dish, slice and serve.
Apple Shortbread Tart https://www.thegratefulgirlcooks.com/apple-shortbread-tart/