How can we reduce the time of cooking?

If you are looking at reducing the overall time to cook a meal, including readying raw materials etc, then the most effective way is to treat cooking like scheduling a project with multiple modules.

For example, I was making some spaghetti last night. It includes the following activities:
Boiling the spaghetti - 20 minsChopping onions - 5 minsFrying onions - 5 minsChopping other vegetables - 10 minsStir-frying onions and vegetables - 10 minsMixing and cooking everything - 10 mins
On the surface it looks like an one-hour activity (20+5+5+10+10+10 = 60 mins).

But:
1, 3, 5 and 6 do not need active involvement; 2 and 4 do5 can only be done last3 can only be done after 2 is done, 5 can only be done after 3 and 4 are done1, 2 and 4 are independent activities (need no prior activities to be completed)
So, in essence, it can be done only in 35 mins.
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Simple rules:
Anything that is happening on its own - boiling, simmering etc.. - should be started first. In case of multiple activities that need manual intervention, start with the one that takes the longest. Do not make too much mess. People spend a lot of time clearing after cooking. I simply spread an old newspaper before starting, and all the waste is simply collected later and dumped (<1 min).Prepare raw material in bulk. Chop up veggies and store half for tomorrow. Having pasta today and tomorrow? Boil double and keep half in the refrigerator. Cook at the optimal temperature. Too low takes too much time; too high risks burning the recipe. Use covered pots and pans as much as possible. Simple 6th grade science - stuff cooks better and faster in a sealed, pressurized container.P.S. Use the last phase (when everything is done, and the meal is getting ready) for other activities like cleaning utensils from before, restocking your fridge, or sit down with your laptop and clean up your mailbox etc. Do not just stand there and wait. :)