Back to my years of childhood in Belgium, I always waited sundays with great excitement for an "éclair" : a vanilla filled "pâte à chou" with a chocolate topping and "muizenstront" (literally mouse poo) or chocolate sprinkles.
You can find them at any bakery in Belgium. The best are the one filled with a pastry bag w/ a fine & long tip. Personally, I found the one cut on the side (to be filled with vanilla) are a shame. It's just the reflection of an impatient baker/pastry chef who doesn't master the art of pastry.
I'll tell you my experience of eclair in France in a future post. Have a nice day!