In a large saucepan, combine the sugar, flour and salt. Stir in milk until smooth. Cook and stir over medium-high heat until thickened and bubbly. Reduce heat; cook and stir 2 minutes longer. Remove from the heat. Stir a small amount of hot filling into egg yolks; return all to the pan, stirring constantly. Bring to a gentle boil; cook and stir 2 minutes longer.
Remove from the heat. Stir in the pumpkin, vanilla, cinnamon, ginger and nutmeg. Transfer to a bowl. Press plastic wrap onto surface of custard. Refrigerate for 2 hours or until cool.
On a lightly floured surface, roll out pastry into a 12-in. x 10-in. rectangle. With a sharp knife, cut into 15 rectangles, 4 in. x 2 in. Place 1 in. apart on ungreased baking sheets. Bake at 375° for 15-20 minutes or until puffed and golden brown. Remove to wire racks to cool.
To assemble, split pastries in half horizontally. Place 10 bottom layers on a work surface; spread each with a scant 2 tablespoons pumpkin custard. Top with 10 pastries, remaining custard and remaining pastries. Sprinkle with confectioners' sugar. Refrigerate for 1-2 hours before serving.