Preheat the oven to 400°F (200°C)
Line a baking sheet with parchment paper
In a saucepan, combine water, milk, butter, sugar, and salt
Bring the mixture to a boil
Add flour all at once and stir vigorously until a dough forms
Cook the dough for 1 to 2 minutes, stirring, until it pulls away from the pan
Transfer the dough to a bowl and let it cool slightly
Beat in eggs one at a time until the dough is smooth and glossy
Spoon or pipe the dough into 4-inch strips on the baking sheet
Bake for 15 minutes
Reduce the oven temperature to 350°F (175°C)
Bake for 20 to 25 minutes more until puffed and golden
Turn off the oven and let the eclairs dry inside for 10 minutes
Remove from the oven and cool completely
Prepare pastry cream or filling of choice
Fill the eclairs with the cream using a piping bag
Melt chocolate for the glaze
Dip or spread the chocolate glaze over the tops of the eclairs
Let the glaze set before serving