Make the Chocolate Glaze
In a medium bowl, melt chocolate in the microwave at 50% power, being careful not to overheat it. Whisk in butter until smooth.

Assemble the chocolate éclairs
With a serrated knife, split éclair shells lengthwise. Spoon a generous amount of the pastry cream into the bottom half of each shell. Dip top half of each shell into the chocolate glaze, close éclairs, and serve.