Combine vinegar and cold water in a jar and put it in the freezer while you make the rest of the dough.
In a large bowl combine flour, salt, baking powder and brown sugar. Add the diced butter to the dry ingredients. With a pastry knive, forks or your fingers mix/cut the butter until it's only pea sized or some smaller. Add 1/4 cup (60ml) of the vinegar water evenlynto the flour-butter mixture and combine to a shaggy dough. Dump everything onto the counter. Carfelly gather the outside shaggy edges and crumbs up and over the top of the dough and press down. Turn and repeat until the dough starts to come togehter. If the dough is too dry and isn't coming togehter, add a bit of vineagr water. If the dough is sticky add a bit of flour. Cut the dough in half, shape into a disk and wrap in plastic wrap and chill in the fridge for 1 hour.
Put almond flour, brown sugar, salt in a food processor and mix. Add the melted butter and egg. process. And then add the honey whiskey and process everything again.
Preaheat oven to 180°C
When the dough is ready roll it out on a lightly floured surface (or directly on the parchment paper) to about 1/4 inch thickness. Transfer to a baking sheet lined with parchment paper.
Spread the fragipane evenly onto dough, leaving a 3 inch (ca 6-7cm) border around the edges. Add the sliced apples. Fold edges over, overlapping slightly. Brush dough with egg wash and sprinkle with brown sugar and cinnamon.
Bake for 40-50 minutes until golden brown. Let cool slightly and serve with some whipped cream or ice cream.