Bake the puff pastry: Set a rack in the center of the oven and heat to 425 degrees. Unfold
t h e s h e e t o f puff pastry o n a piece of
parchment paper s e t i n a rimmed baking
sheet. Bake until puffed and brown, about 1 0
minutes. Reduce t h e heat t o 3 5 0 degrees and continue baking until dry, crisp and deeply
browned, rotating the baking sheet once
during baking, 2 0 t o 3 0 minutes. (Once
cooled, pastry can b e covered and stored a t
room temperature f o r u p t o 3 days.)
Make the filling: I n a medium bowl, combine
t h e granulated sugar, butter a n d kosher salt.
Stir together with a wooden spoon o r stiff
silicone spatula until evenly combined a n d
creamy. Add t h e almond flour, egg, r u m and
almond extract; whisk until evenly combined.
(Filling can b e stored in a n airtight container
a n d refrigerated for u p t o 3 days.)
When ready t o assemble, heat t h e oven to 350 degrees. Using a long, sharp serrated
knife, carefully slice t h e puff pastry
horizontally, splitting i t a s you would a bagel.
Flip the top of the pastry over, then spread
a b o u t two-thirds o f t h e a l m o n d filling evenly across t h e bottom of it, taking care t o spread i t all t h e way t o t h e e d g e s . Flip t h e t o p piece of pastry back onto t h e bottom piece, then evenly spread t h e remaining almond filling on top. Evenly distribute t h e sliced almonds o n top, then lightly sprinkle with flaky salt. Bake until t h e n u t s a r e t o a s t e d a n d t h e topping is brown, rotating the baking sheet once during baking, 20 to 2 5 minutes.
Let cool slightly, t h e n u s e t h e parchment to slide t h e pastry o n t o a cutting board. Dust
generously with confectioners' sugar, then
slice into portions with a s h a r p knife. Serve
w a r m o r a t r o o m t e m p e r a t u r e .
Tips
The b e s t way t o t h a w frozen puff pastry i s t o l e t it sit overnight in t h e refrigerator. However, if you're in a hurry, you can thaw it on t h e counter until i t unfolds easily b u t i s still quite cold. If the pastry gets too warm and soft, pop it in the fridge t o firm u p before using.
M a k e s u r e t o u s e b l a n c h e d a l m o n d flour r a t h e r than the unblanched kind, which is made with natural almonds and includes their skins; unblanched almond flour will m a k e t h e filling too stiff to spread properly
