In a large bowl, add both boxes of instant vanilla pudding mix. Add cream, then milk, 1/2 cup at a time, combining well after each addition and making sure that no lumps remain.
Add vanilla and stir well to combine.
Using a pastry decorating tool--my personal favorite is the gun-style pastry tool, because it's so much easier to use--fill each pastry with vanilla filling.
Coat the top of each éclair with a thin layer of chocolate frosting.
Any eclairs not consumed immediately should be refrigerated or frozen. Remember, the pudding contains milk and cream, so is likely to spoil quickly if left out for too long.