Preheat your oven to 450°F. Melt the 1/2 cup butter in a medium saucepan over medium heat.

Once the butter is melted, add water and bring to a boil over high heat. Lower the heat and add salt, then gradually mix in the flour, stirring quickly until the dough forms a ball and doesn't stick to the pan. Remove from heat.

Add the eggs one at a time, whisking each until fully incorporated.

On a greased or parchment-lined cookie sheet, spoon the dough into 1-inch by 3-inch strips.

Bake for 15 minutes, then reduce the oven temperature to 325°F and bake for another 20 minutes. Tap the bottom of an eclair with a spoon; if it sounds hollow, they're done. If not, bake for another 3-5 minutes.

Cool the eclairs on a wire rack.

In a medium saucepan, heat the milk until it simmers, stirring regularly.

In a separate bowl, mix the sugar, cornstarch, and salt. Add the egg yolks and mix until smooth and creamy.

Gradually whisk in the hot milk to prevent the eggs from curdling.

Return the mixture to the saucepan and boil for 30 seconds until it thickens to a pudding-like consistency.

Stir in 7 tablespoons of butter and the vanilla extract until smooth. Gently rub the remaining butter on the top, cover with plastic wrap, and refrigerate for 1-2 hours.

Transfer the filling to a piping bag. Poke a hole in the bottom of each eclair shell and fill.

In a microwave-safe bowl, melt the chocolate chips and 2 tablespoons of butter in 30-second intervals, stirring each time until smooth.

Mix in the powdered sugar and vanilla extract until well combined.

Add boiling water, one tablespoon at a time, until the icing is smooth.

Dip the tops of the eclairs into the chocolate icing and let any excess drip off.

Refrigerate for at least 30 minutes before serving.