Preheat oven to 350°F (177°C)
Toast almonds: spread almonds in a single layer on a baking sheet and toast in the oven for 6 - 8 minutes until golden and fragrant. Remove and set aside to cool.
Heat amaretto either in a small pot or in the microwave and add golden raisins to the amaretto to soak.
In a medium mixing bowl, whisk together flour, baking powder and salt. Set aside.
In a separate medium mixing bowl, whisk together sugar, cooled butter, vanilla and eggs.
Add golden raisins with amaretto and toasted almonds.
Add flour mixture to egg mixture and stir just to combine.
Cover dough and chill 30 -45 minutes.
Divide dough in half and shape into two equal-sized rectangles.
Whisk water with remaining egg and egg wash the dough.
Combine coarse sugar and flake salt, sprinkle the top of the loaves with sugar salt mixture.
Bake for 30 minutes, rotating tray halfway through.
Cool for 15 minutes, then carefully slice biscotti loaves into 1/2" slices.
Place biscotti slices back on baking sheet, cut sides down, and bake for an additional 15 minutes.
Cool completely on wire rack.