Heat water, milk, butter, sugar, and salt in saucepan until boiling.

Add flour all at once and stir until dough forms and leaves pan sides.

Cook dough 1–2 minutes, then cool slightly in bowl.

Beat in eggs one at a time until smooth glossy dough forms.

Pipe 4–5 inch logs onto tray with space between.

Bake 30–35 minutes until puffed and golden, then cool completely.

Whisk egg yolks, sugar, and cornstarch for filling in bowl.

Heat milk until steaming and whisk slowly into yolk mixture.

Return mixture to pan and cook until thick custard forms.

Stir in butter and vanilla and cool fully.

Fill éclair shells with cream using piping bag.

Heat cream and pour over chopped chocolate to make glaze.

Dip tops of filled éclairs into chocolate glaze and set.