How to get fried prawns to be juicy

It sounds to me like the issue may be that you're crowding the pan.

Basically, to get everything nice and brown and crispy, you need enough space for all of the steam to escape. That picture you showed has potatoes stacked on top of each other -- that means as the bottom items cook, they're going to end up steaming the items above them.

At a diner, they have a large griddle to work with -- they can really spread things out. You're not typically that lucky in a regular kitchen, as you don't have as much space, and you have a lip on the pans that'll hold the steam in.

So, either work in smaller batches, or consider recipes that use an oven -- using sheet pans instead of a pan on the stove solves much of the problem.

One other trick is that most diners don't start from raw potatoes -- maybe with hash browns, but not for home fries, you're not going to get the nice soft interior in a reasonable amount of time unless you start with a potato that's already been baked or boiled. (If you're doing things in the oven, you might be able to, but not in a pan)

Just for reference ... I have a 14" cast iron skillet that I use for home fries ... and it's about the right size for cooking a single large potato, which might be two servings, maybe three for kids. (I tend to cook carb-heavy meals).

update : I probably should've stated this directly -- you want the chunks of potato to form a single layer in the pan, with space in between them.

Induction just heats the pan using magnetism. Aside from very high efficiency, it isn't so different from any other method, and how hot the oil gets is an issue of power output and heat transfer/conductivity of the pan itself. There isn't an appreciable difference in how the physics work inside the pan.

Clearly your oil is not hot enough for frying/sautéeing. Most induction cooktops say they draw at least 1000 W to produce temperatures in the 350-400° F range, which is a somewhat typical frying temperature, being just at or below the smoke points of most oils. However, that number is based on a lot of assumptions, and 1500 W is not necessarily a generous margin of error for a portable hot plate. A lot of things could prevent you from reaching even a modest 400° F:

• The pan is too dense. Are you using cast iron? It responds well to induction but the thermal resistance is also a lot higher.

• The pan is very large and/or you're stuffing a lot of food into it, a result of which could be that the heat is escaping faster than the hot plate can pump it out.

• The pan does not actually have the right amount of magnetic permeability for high-heat cooking. A magnet may stick to it, but how hard does it stick? If there isn't a very strong attraction - i.e. you have to put some effort into pulling off a permanent magnet - then you're not getting anywhere near the efficiency the unit was designed for, and even the full 1500 W may not be enough to reach the desired temperatures.

• The cooktop is not really pulling in the full 1500 W, either due to a poor power source or simply poor design. Some manufacturers might quote 1500 W as a peak in order to sell more units, knowing full well that they can't sustain more than about 60% of that. If you've got a power meter (e.g. Kill-A-Watt), plug it in and see how much it's really drawing.

There are some portable induction cookers that go up to 1800 or even 2000 W, which is the bare minimum for the large element on an electric or induction stove (2500 W is typical for those). If you want to use a portable hot plate for high-heat cooking, check your pans very carefully, don't overcrowd them, and if all else fails, you might just need a better hot plate.