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How can you get the golden-brown colour and fabulous aroma by cooking food?

Temperature is the trick.

And by temperature I really do mean high temperature. Chemically it's something called caramelisation reaction, which occurs when we heat food in an oven, grill or oiled frying pan up to around 160^oC. That doesn't mean we get nothing below 160^oC. By the time the temperature rises to 140^oC, it will kick start another set of Maillard reaction. These reactions between proteins and sugars explain the secret of many cooks. Brushing a little egg white on the surface of flour, I was told, provides extra protein to react with carbohydrates, helping it brown and adding taste. Notice how much we love the freshly baked bread after these reactions in the oven. 

So now I know why cooking food in a microwave oven doesn't work wonder. In the case of the microwaves, they are tuned to the vibration frequency of water molecules. The heat comes directly from the water in the food, whereas caramelisation and Maillard reactions only happen with dry heat. Alas, without these miraculous reactions, the tasty aroma molecules won't appear.

Take one more look at these reactions in the kitchen, and then outside. You'll see a similar thread of theory around us. There are similar reactions around, whatever your subject. Take final year medical students; once sitting in the library and reading lecture notes only, they now are mandated to go to the medical wards and work as part of a team - in the form of apprenticeship. One tried and tested method is to give them a quota. That means the students have to see a minimum number of new patients, and take blood from, say, no less than six patients. We'd like to aim high and let the students work hard, more or less like achieving the temperature of 140^oC. That is really tough when you compare to spoonfeeding in the classroom (the microwave-equivalent in the kitchen). But, at the end, we hope it will give them a glimmer of golden-brown splendour.

How high should we raise the bar? I don't have the right answer but I remember another important rule in cooking: less desirable molecules can appear after too high a temperature. Go beyond 200^oC, and be prepared to get the bitter-tasting carcinogenic stuff.