Source: The Great Interpretation of Dreams (Ibn Sirin)
The brain in a dream is the intellect and stored wealth. Eating it indicates gaining the wealth of a leader or the death of that leader.
Source: Perfuming Humanity in the Expression of Dreams (Al-Nabulsi)
The brain indicates the wealth that a person relies on for his strength. Whoever sees his brain grow larger, his wealth and intellect will increase.
Source: Signs in the Science of Expressions (Ibn Shaheen)
The brain is interpreted as wealth. Whoever sees himself eating it will gain wealth.