Filling**** cook pudding according to pkg. Cool 1 hr.
Pastry**** In sauce pan heat butter, water, and salt over med heat until mixture boils and butter melts. Reduce heat to low. Vigorously stir in flour all at once until mixture forms a ball. Transfer pastry to a bowl: Stir in eggs; one at a time, beating well after each. Preheat oven to 400*. Grease a baking sheet. Drop dough into dozen mounds, about 13 cm apart, Spread each mound into 4x 1 cm rectangle, piling dough on top and slightly rounding sides. Bake until golden, 35 minutes. Remove from oven; make 3 cm slit on side of each eclair. Reduce oven to 375* and bake for 10 minutes more. Transfer to wire rack to cool.
Frosting***** heat butter and chocolate over low heat, stiring until melted. Remove from heat, stir in sugar, milk, and vanilla until smooth.
Slice eclairs in half. Spoon about 1 tablespoon of filling onto each bottom half and replace tops. Spread tops with frosting.