1-Preheat: Set your oven to 400°F (200°C) and line baking sheets with parchment paper.

2-Combine liquids and butter: In a medium saucepan, bring together ½ cup water, ½ cup whole milk, 8 tablespoons unsalted butter, 1 teaspoon sugar, and ¼ teaspoon salt. Heat until the mixture boils and butter melts.

3-Add flour: Remove from heat. Quickly stir in 1 cup flour all at once, mixing vigorously until the mixture forms a smooth dough and pulls away from the pan.

4-Incorporate eggs: Transfer dough to a bowl and cool to below 160°F (70°C). Beat in 4 large eggs one at a time on medium speed, fully incorporating each before adding the next to create thick, glossy dough.

5-Pipe dough: Using a piping bag fitted with a ½-inch French star tip, pipe 4-inch logs spaced 1.5 to 2 inches apart on lined baking sheets. Optionally smooth peaks with a wet finger and lightly dust with powdered sugar.

6-Bake: Bake at 425°F (220°C) for 10 minutes to puff, then reduce temperature to 325°F (160°C) and bake 30-40 minutes until golden and hollow sounding when tapped. Avoid opening the oven early. Near the end, prick shells with a toothpick to release steam and promote crispness.

7-Cool: Remove eclairs and cool completely on wire racks.

8-Prepare pastry cream: Heat 2 cups whole milk with vanilla bean seeds or extract. In a bowl, whisk ¾ cup sugar, ¼ cup cornstarch, pinch of salt, and 4 egg yolks until smooth. Temper yolks with hot milk, then cook gently until thickened. Stir in butter, cover surface with plastic wrap, and chill.

9-Fill eclairs: Pierce holes in the bottom of each shell and fill generously with chilled pastry cream using a piping bag.

10-Make glaze: Heat ½ cup cream and optional salt until simmering, pour over chopped chocolate. Let rest 2 minutes, whisk smooth, reheat if needed.

11-Glaze tops: Dip each filled eclair top into the warm chocolate glaze and set on racks until glaze firms.

12-Serve: Enjoy immediately or refrigerate briefly. For best texture, consume within one day.