Éclairs

Name: Éclairs
Ingredients: 1/2 cup milk; 1/2 cup water; 1/4 cup plus 3 tablespoons (3 1/2 ounces) unsalted butter; 1 tablespoon sugar; 1 teaspoon kosher salt; 1 1/2 cups (7 ounces) all-purpose flour; 1 large egg whisked with 2 tablespoons water; 4 cups Pastry Cream (recipe follows); 1 1/2 to 2 cups Chocolate Ganache; Pastry Cream:; 2 cups whole milk; 1/2 vanilla bean, split and scraped; 7 large egg yolks; 1/2 cup (3 1/2 ounces) sugar; 2 tablespoons (3/4 ounce) cornstarch; 2 tablespoons unsalted butter, at room temperature; Chocolate Ganache:; 10 ounces 62 percent cacao chocolate, chopped; 2/3 cup (2 1/2 ounces) sifted powdered sugar; 3/4 cup plus 1 tablespoon heavy cream; 2 large egg yolks; 3 tablespoons unsalted butter, at room temperature