"When you talk about eclairs, homemade is always a better option. Bakery-bought eclairs mostly have soggy and mushy crusts, because bakers freeze their choux pastries for days. Therefore you're better off baking and filling them fresh at home."
Preheat the oven to 425 degrees F (220 degrees C). Butter a baking sheet.
Heat 3/4 cup plus 1 1/2 tablespoons water, 8 1/2 tablespoons butter, and salt in a saucepan over medium heat. Bring to a boil; turn off the heat and sift in flour. Beat vigorously with a wooden spoon until mixture is well combined and leaves the sides of the pan.
Cool the mixture to room temperature, about 10 minutes. Crack in eggs, 1 at a time, stirring gradually into a smooth dough. Lift the spoon to check the consistency; dough should slide gradually back into the bowl.
Fit a piping bag with a coupler and 3/4-inch round nozzle. Drop piping bag, nozzle-down, into a tall glass and fold edges down around the glass. Spoon dough into the bag. Gather edges and twist together.
Pipe dough into 5-inch-long logs onto the prepared baking sheet. Press logs down with wet fingers if any peaks form.
Bake in the preheated oven until golden and firm, 30 to 35 minutes. Let eclairs cool on a wire rack while preparing the topping and filling.
Place chocolate and 1/4 cup butter in the top of a double boiler over simmering water. Stir frequently, scraping down the sides with a rubber spatula to avoid scorching, until chocolate is melted, about 5 minutes. Remove from heat.
Beat cream in a chilled glass or metal bowl using an electric mixer until frothy. Add confectioners' sugar and vanilla extract gradually, continuing to beat until stiff peaks form. Fill a clean piping bag with the whipped cream.
Use a paring knife to cut an X in either end of each eclair. Pipe a portion of the whipped cream into one end of each eclair until it starts to ooze out the other side. Dip the top halves in melted chocolate-butter mixture. Refrigerate eclairs until filling hardens, about 30 minutes.