Cool completely on a wire rack. For the filling, combine pudding mix and milk in medium bowl according to package directions. In a separate bowl, beat the cream with an electric mixer until soft peaks form. Fold whipped cream into pudding. Cut tops off of cooled pastry shells with a sharp knife.
Fill shells with pudding mixture and replace tops.
For the icing, melt the chocolate and 2 tablespoons butter in a medium saucepan over low heat. Stir in 1 cup confectioners' sugar and 1 teaspoon vanilla. Stir in hot water, one tablespoon at at time, until icing is smooth and has reached desired consistency. Remove from heat, cool slightly, and drizzle over filled eclairs. Refrigerate until serving.