Make a slit along the back of each prawn. Season the prawns with garlic, salt and white pepper. Chill for 20 minutes.
Lightly dredge the prawns with cornflour. Heat a large frying pan with butter over medium heat. Fry the prawns until they are no longer translucent, about 4-6 minutes, set aside.
Heat the same pan with butter over medium heat. Saute the garlic until aromatic, 2-3 minutes. Reduce the heat to low, stir in the egg yolks and cook for 2 minutes. Stir in the prawns an mix well. Garnish with spring onions before serving.
Salted eggs can be found in Chinese/Oriental speciality stores.