Thinly slice the onions. 

Add the sliced onion into the hot tallow and sauté it on medium-high heat until it gets a glassy / translucent look. 

Reduce the heat to medium and throw in the black pepper and garlic. 

 Sauté the garlic until fragrant for about 2-3 minutes. 

Dice up the brains. 

Put the diced-up brains onto the onion. 

Sauté the onions and brains on medium-high heat until the brains changes color to whitish for about 2-3 minutes 

Pour the lightly beaten eggs into the pan as well. 

Fry the eggs and brains to taste.