Start by heating the sugar and water in a 3-quart pot over medium heat. Swirl the pan gently, but do not stir it, until a candy thermometer reads 230°F.

Next, stir in the almond flour, egg whites, and salt. Cook for 3 minutes, stirring constantly. Then remove the pot from the heat and stir in the almond extract. Press the mixture through a mesh sieve into a bowl to eliminate tiny scrambled egg bits.

Gradually stir in the sifted powdered sugar until the mixture becomes a soft, moldable dough.

Heat the oven to 425°F and line a baking sheet with parchment paper or a silicone mat. Roll the puff pastry on a floured surface to about 11 by 13 inches, then cut it into two 5 1/2 by 13-inch rectangles.

Divide the marzipan into two equal parts and shape each into a log about 10 1/2 inches long. Set one log on each pastry strip. Brush the edges with egg wash, fold the ends over, and roll the pastry around the filling. Place both logs seam-side down on the baking sheet and chill for 20 minutes.

Brush the tops with egg wash, then sprinkle with sliced almonds and granulated sugar. Bake for approximately 22 minutes, or until the pastry is puffed and golden. Let cool completely before slicing into 20 pieces.