1. Prepare the Pate a Choux. Whisk together egg and 1 tablespoon water in a small bowl for an egg wash. Set aside. Preheat oven to 375 degrees, with racks in upper and lower thirds.

2. Line two large baking sheets with parchment paper. With a ruler and a pencil, mark lines about 3 1/2 inches long on the parchment, spacing them about 1 1/2 inches apart. Turn parchment over, marked sides down. Fill a pastry bag fitted with a 5/8-inch plain tip with Pate a Choux; pipe along the lines on the prepared baking sheets. Gently smooth tops with a moistened fingertip to ensure even rising. Brush the top of each eclair with egg wash.

3. Bake until pastries are golden brown, 25 to 30 minutes. Transfer pastries and parchment to wire rack to cool completely.

4. Make the pastry cream: Scrape the seeds from the vanilla bean. In a heavy saucepan, combine milk, vanilla bean and seeds, and 1/2 cup sugar. Scald the mixture and immediately remove from heat.

5. Beat egg yolks with remaining 2 tablespoons sugar until thick. Sprinkle in flour and cornstarch and continue beating until mixed.

6. Beat half of the hot milk into yolk mixture. Return this to the remaining hot milk and bring to a boil quickly, whisking very fast to prevent scorching. Remove from heat and strain into a bowl to cool. Stir in butter. Cover with plastic wrap, pressing directly on the surface of the pastry cream to prevent a skin from forming. Transfer to the refrigerator to chill completely. Immediately before using, gently fold in softly whipped cream with a spatula.

7. To fill the pastries, insert a wooden skewer into both ends of each shell. (You can also use a small pastry tip, such as the one you will use for filling, to create the holes.)

8. Transfer pastry cream to a pastry bag fitted with a 1/8-inch plain tip, preferably one that is long and skinny. Insert the tip into the end of each pastry, and pipe to fill with pastry cream (filling the shell with pastry cream from both ends will insure a properly filled eclair).

9. Make the glaze: In a small bowl, whisk to combine heavy cream, espresso powder, and maple syrup. Add confectioners' sugar and whisk until smooth, thinning with additional heavy cream if necessary.

10. Dip the top of each eclair into the maple espresso glaze; let excess drip off, and place, coated side up, on a wire rack set over a rimmed baking sheet. Refrigerate eclairs in a single layer until glaze is set, about 10 minutes, and serve.