Preheat oven to 425°. Line 2 rimmed baking sheets with parchment paper. Draw 3 (2½-inch) lines 3 inches apart on parchment paper; turn parchment paper over.
In a medium saucepan, bring milk, butter, salt, and sugar to a boil together over medium-high heat. Reduce to heat to low; add flour, stirring with a wooden spoon until a dough forms, approximately 2 minutes.
Turn out dough into the bowl of a stand mixer fitted with the paddle attachment. Let cool for 1 minute.
With mixer at medium speed, beat in eggs and egg yolk, one at a time, until thoroughly incorporated. Beat for 2 minutes after adding last egg.
Transfer dough to a pastry bag fitted with a large open-star tip (Ateco #826). Pipe dough onto drawn lines on prepared baking sheets. Wet your fingertip to smooth down ends of éclairs.
Immediately reduce oven temperature to 375°, and bake for 15 minutes. Reduce oven temperature to 350°, and bake 15 minutes more. Let cool completely on wire racks.
Using a sharp knife, cut each éclair in half lengthwise.
Melt dipping chocolate according to package directions. Dip top half of éclairs in melted chocolate. Let chocolate set.
Place Keemun Pastry Cream in a piping bag fitted with a large open-star tip (Ateco #826). Pipe cream onto bottom half of éclairs. Top with chocolate-dipped tops, pressing down gently.
Notes
We used Ghirardelli Dark Melting Wafers.
Recipe by TeaTime Magazine at https://teatimemagazine.com/keemun-eclairs/