In a saucepan add water, butter, shortening, powdered milk, and salt and bring to a boil. When boiling, add the pastry flour and mix well. Pour these ingredients into a standing mixer with a whisk attachment and add the eggs, 1 at a time. Mix until all ingredients are combined well. Remove the batter from the mixer and pour into a pastry bag. Using a small tip, pipe the batter out about 2 inches long onto a baking sheet covered with parchment paper. Bake at 350 for 45 to 50 minutes.
In a small saucepan mix together the milk, 1/4 cup sugar, the butter and vanilla bean scrapings and bring it to a boil. In a medium bowl whisk together the remaining 1/4 cup sugar with the cornstarch. Add the eggs and yolks and mix until well combined. Temper the hot milk mixture into the egg mixture and add combined mixture back into the hot milk. Bring the pastry cream to a boil. Remove from the heat and strain it through a fine sieve into a medium bowl. Cover with plastic wrap that touches the cream itself. Refrigerate until ready to use. Pastry cream will stay fresh covered and refrigerated for up to 1 week. Yield: approximately 4 cups
Place the filling into a pastry bag and using a small tip, fill the center of the Eclair.