Brocho before eating this: Take a Crispix and split it. Say Borei Minei Mezonos and eat the darker side, and then say Borei Pri Ha'adama and eat the lighter side.

Brocho after eating the proper shiur of this: Borei Nefashos

Source: Star-K Cereal List

Note: Halachically Speaking (volume 4, issue 2) says that the custom is to say Shehakol Niyeh Bedvoro