Place the butter and almond flour in the bowl of a stand mixer fitted with the whisk attachment and whip until creamy. Turn off the machine and add the brown sugar. Turn the mixer on low and gradually increase the speed to blend in the sugar. Slow the mixer again, add one of the eggs, and beat until creamy. Add the flour with the machine off, then mix just until it is incorporated. Finish mixing in the flour by hand, using a rubber spatula if needed. (Hand mixing is more thorough, as the electric mixer does not reach the edges of the bowl very well.) Cover the bowl of almond cream with plastic wrap, and leave it out at room temperature.
Cut the puff pastry in half. On a lightly floured work surface, roll each piece of dough into a a circle 1/8 inch thick. If the dough sticks to the rolling pin, sprinkle it lightly with flour. Using a 9-inch plate as a guide,, cut out a 9-inch circle from each piece of dough. Transfer each puff pastry circle to a parchment-lined sheet pan. Refrigerate for 30 minutes.
Beat the remaining egg with the salt to make a wash. Scrape the almond cream into the middle of one of the circles. Using an offset spatula, spread the cream evenly, leaving a 1 1/2-inch border. With a pastry brush, brush he border with egg wash. Place the remaining dough circle on top of the almond cream. Press the two dough circles together at the edges to create a seal.
Brush the top of the galette with the rest of the egg wash. Using a sharp, pointed knife or a pastry tip, cut or punch a few holes in the top layer of dough to allow steam to escape as the pastry bakes. Refrigerate the galette for 3 hours to let the dough rest.
Preheat the oven to 325 degrees. Two hours before serving time, bake the pastry for 1 hour. Warm the jam in a small saucepan or in the microwave to make a glaze. When you remove the galette from the oven, brush it with the glaze to create a shiny finish.
Cool for 1 hour before serving.
Reprinted with permission from ©Sweet Magic: Easy Recipes for Delectable Desserts, by Michel Richard with Peter Kaminsky, published by Harper Collins click for book review