1) Preheat the oven to 400°F. Lightly grease a baking sheet, or line it with parchment.
2) Divide the pastry in half, and roll each piece into an 11" square.
3) Using a 10"-round template, cut a 10" circle from one piece, and an 11" circle from the other.
4) To make the filling: Beat the almond paste, butter, sugar, and salt until creamy.
5) Add the egg yolks and vanilla, and beat until well incorporated.
6) Mix in the flours.
7) To assemble the galette: Spread the filling over the smaller circle, leaving a 1" rim around the edge of the pastry.
8) To make the glaze: Mix the egg yolk and water together. Brush some glaze over the uncovered edge of the pastry.
9) Center the larger round of dough over the filled bottom crust, and smooth it over the filling. Using a fork, press and crimp the rim of the galette to seal.
10) Decorate the galette, using the back of a knife to trace a pattern on the surface; poke five vent holes, and brush with the remaining glaze.
11) Bake the galette for 30 to 35 minutes, or until it's golden. Remove it from the oven, and cool before serving.
Yield: one 10" galette, about 12 servings.