For the shortcrust dough:
1. In the bowl of a standing mixer, beat butter, salt, corn syrup and sugar for 4-5 minutes until light and smooth.
2. Scrape the sides and bottom of the bowl. On low speed, add the beaten egg. Mix until fully incorporated. Add vanilla, then flour 1/2 cup at a time. Mix until you have a soft, smooth dough. Do not over-mix!
3. Wrap the dough in plastic wrap and refrigerate overnight. Remove from the refrigerator 10-15 minutes before baking.
For the apple filling:
1. Peel and slice apples into 1/8-inch cubes. Coat with lemon juice, then place into a pan over medium heat. Once apples start to boil, reduce to a simmer and cook for 3-4 minutes.
2. Strain apples into a bowl, leaving the liquid in the pan. Add sugar and cinnamon to the liquid and stir until the sugar dissolves.
3. Mix potato starch with 1/4 cup water and add to the pan. Once thickened, re-add apples, remove from heat and blend. Allow to cool until room temperature.
For the meringue:
1. Place egg whites and salt into the bowl of a standing mixer fitted with the whisk attachment. Gradually increase speed to high and beat until frothy.
2. Reduce speed to low-medium and slowly sprinkle in sugar.
3. Return speed to high and beat for 4-5 minutes until you have a shiny, strong meringue.
1. Preheat oven to 350 F.
2. Line a 13-by-9 baking pan with parchment paper and grease the sides. Flatten shortcrust dough evenly inside baking pan. Using a fork, prick it thoroughly. Bake for 12-14 minutes until the sides of the pastry are starting to lightly brown.
3. Remove from oven and let cool in the pan for 15-20 minutes. Note: Make the meringue at this point.
4. Evenly spread apple filling on top of baked dough and top it with meringue. Sprinkle with almonds.
5. Bake for 15-20 minutes or until the meringue is evenly golden on top. Let cool completely before slicing.