Step 1Measure 1 cup water, the butter and salt into a heavy saucepan. Bring to a boil. When the butter is melted, remove the pan from the heat and add the flour all at once. Stir vigorously with a wooden spoon until completely mixed and blended.
Step 2Return to the heat and cook and stir over low heat 5 to 6 minutes, to dry the mixture. The dough should be soft and should not stick to your fingers when pinched. The bottom of the pan should be covered with a thin crust, which is an indication that the dough has been sufficiently dried.
Step 3Transfer the dough to a bowl and let it cool for at least 5 minutes. Add 4 eggs one at a time, beating carefully after each addition so that the mixture is smooth before the next egg is added. The dough should be smooth, shiny and as thick and heavy as mayonnaise.
Step 4Heat the oven to 400 degrees. Coat a cookie sheet with butter and flour. Using a flan ring or any circular mold, mark an outline about 10 inches in diameter.
Step 5Spoon the pate a choux into a pastry bag. Squeeze out a ring about 1 inch wide following the outline. Squeeze another ring inside the first, then squeeze a ring on top of the others.
Step 6Brush with remaining egg, lightly beaten. Sprinkle with sliced almonds. Let choux stand about 20 minutes.
Step 7Bake 45 minutes. Turn off the oven and open the oven partially. Let the ring stand in the oven for 1 hour so it cools and dries.
Step 1For the nougatine, combine 1 cup powdered sugar and almonds in a heavy saucepan. Stir with a wooden spoon. Place on medium low heat and cook, stirring constantly, until the sugar starts to melt. Since there is no liquid in the mixture, it will take a few minutes, about 3 to 4. As soon as it melts, it will turn rapidly into caramel. As soon as this happens, pour the mixture onto an oiled marble or an oiled tray. When cold, break into pieces and blend into powder in a food processor or blender. Set aside until ready to fold into the creme patissiere.
Step 2For the creme patissiere, heat the milk to boiling, then set aside. Combine the egg yolks, sugar and vanilla in a bowl and beat with a wire whisk until it forms a ribbon, 3 to 4 minutes. Add the flour and mix thoroughly.
Step 3Add half the hot milk to the egg mixture and return all to the remaining milk. Bring to a boil over medium heat, stirring constantly. The sauce will thicken as soon as it reaches the boiling point. Reduce the heat and cook for 2 to 3 minutes, stirring constantly to avoid scorching.
Step 4Pour the creme patissiere into a bowl and cover with plastic wrap to avoid a skin forming on top. Place in an ice water bath to cool. Cool to room temperature. Fold powdered nougatine into creme patissiere.
Step 5Use a long bladed knife and cut the lid off the choux pastry ring.
Step 6Whip the cream until stiff. Fold in 1 tablespoon powdered sugar.
Step 7Fill the bottom part of the ring with creme praline. Pipe slightly sweetened whipped cream over the top of the custard. Place the lid back on top.
Step 8Sprinkle with the remaining 1 tablespoon powdered sugar. Cut into wedges with a serrated knife.