Heat a 28cm or 11" frying pan a medium heat and add the oil and onions. Cook gently for 10 minutes; you do not want to add any colour.
Peel and finely slice the garlic, add it to the softened onions and cook for a further minute.
Add the flour and stir for 60-90 seconds to begin cooking it out.
Add the remaining ingredients for the sauce and simmer gently for 15-20 minutes.
When the sauce has cooked and has a nice texture, I like to blend and pass it through a fine-mesh sieve; this step is optional.
If your prawns are frozen, defrost them by running them under cold water for 3-5 minutes.
Devien the prawns then thread them onto skewers, starting at the head end. This will keep them straight when they are fried. This is an optional step, and it is mainly aesthetic.
Place the flour in a small bowl, add the eggs, salt and pepper to a second bowl and beat lightly and finally add the panko breadcrumbs to a final bowl.
Dip the prawns into the flour, then into the egg and finally coat in the breadcrumbs. Repeat until all of the prawns are coated.
Heat 6-7mm (¼") of oil in the base of a 30cm or 12" frying pan until it reaches around 160°C or 320°F, add the prawns and fry them for 2-3 minutes on each side and serve immediately.