Prepare pudding with milk according to package directions. Chill 1 hour in refrigerator.
Preheat oven to 400 degrees F (200 degrees C). Grease baking sheets.
In a heavy saucepan, combine 1/2 cup butter, water and salt over medium-high heat. Bring to a boil, then reduce heat to low. Pour in flour all at once and stir vigorously until fully incorporated and mixture forms a ball. Remove from heat, let rest 5 minutes. Then beat in eggs, one at a time, until well combined.
Drop dough into twelve equal mounds on baking sheets. Spread each mound into a 4x1/2 inch rectangle.
Bake in preheated oven 35 minutes, until golden. Remove from oven and make a one-inch slit in the side of each eclair. Reduce heat to 375 degrees F (190 degrees C). Return eclairs to oven for 10 minutes. Transfer to a wire rack to cool completely.
Prepare icing while eclairs are cooling. Heat 2 tablespoons butter with chocolate in a small saucepan over medium heat, stirring until melted. Remove from heat and stir in confectioners' sugar, 2 tablespoons milk and vanilla. Set aside.
To assemble: Slice each eclair in half lengthwise. Spoon about 1 tablespoon chocolate pudding into the bottom half of each eclair. Replace tops and frost with chocolate icing. Chill until serving.
