Preheat oven to 350° F or 325° F convection.
Prepare a baking sheet by lining with parchment paper. Have a large zip-top bag ready for piping dough.
Whisk together the gfJules Flour and salt in a small bowl and set aside.
In a mixing bowl, cut the cold butter into smaller pieces and cream together with sugar until light and fluffy – at least 2-3 minutes. Add the extracts and beat again to integrate.
Add applesauce or egg, alternating with the blended gfJules Flour/salt mixture; beat just until a stiff dough forms.
Scoop dough into the zip-top bag and squeeze it into the bottom of the bag. Cut off a 1-inch diagonal from one corner of the bag. Squeeze dough out of the corner to form even 2 inch long cookies. They will not spread very much, so you can line up cookies to fill the cookie sheet, leaving only and inch or so in between them, if need be.
Once all the cookies are piped out, wet your fingers or a rubber spatula and go over the cookies lightly to press them flatter and smooth out the ends. The flatter they are before they go into the oven, the crunchier they'll be once baked, so decide if you want crunchier or chewier cookies.
Bake in preheated oven for 15 minutes, then check to see if the bottoms are lightly browning. If not brown yet, return to the oven and continue to bake for another 2-4 minutes, watching to make sure the cookies do not get too brown.
Remove to cool on a wire rack.
Select pairs of cookies which are approximately equal in width and length and arrange together so they are ready for the chocolate.
Once fully cooled, melt chocolate in a double boiler, chocolate pot, or glass bowl in a microwave (approximately 1 ½ minutes, depending on microwave strength), stirring frequently to ensure the chocolate does not burn. If adding flavored extract to the chocolate, whisk it into the melted chocolate once smooth.
Using an offset spatula or butter knife, apply melted chocolate to the underneath side of one of each pair of matched cookies. At first, the chocolate will be shiny; as it cools, it will no longer be shiny.
Press a matching cookie on top of each chocolate-topped cookie just before the chocolate is no longer shiny. By waiting until then, the chocolate will have mostly set and won’t run out the sides of the cookies when pressed together, but it will still be warm enough to melt into the top cookie.
Store cookies in an airtight container for up to 5 days.