Aero

Aero Milk Chocolate is kind to the teeth. This delicious new chocolate is easy to bite. It has a texture like honeycomb: crisp and yielding. Because of this special texture, Aero digests more quickly, and consequently gives you energy faster than any other chocolate you can buy. It's a bigger block, too - you get more for your 2d.
Source: Picture Post. November 11, 1939