In medieval times in the west, cooking involved stirring things together and baking them. It was slow work, done by hand. Many bakers worked, because it wasn't practical for the average person to spend 6 hours a day stirring bowls of bread dough and shoving it in an oven. (Yes, there were other cooks that made things that weren't bread, pastry, and cake, but these were the big staples. A very large number of people could barely afford bread, pastry, and cake on holidays.)
Today, there are still bakers, but many of them have been replaced with mixing machines and food processors, because paying someone else to cook your food is expensive and annoying. We don't mind the slight loss of unemployment, because being a medieval baker sucked. Being a modern baker is significantly more fun, because now you can create loads and loads of food that many people will eat, instead of working 12 hours a day just to feed one village.
What else could be done to help out in the kitchen? Certainly more than the existing works, which help prepare the food, but can't help anymore once the heat is applied.
Let's start with ingredient selection. Raw ingredients can be kept in pneumatic tubes and delivered from a signal. Ingredients that should be stored cold would start in a refrigerated area, of course.
An auto-stirring device would be appreciated, I reason from my own experience. Many foods need significant stirring as to not burn on the bottom of the pan and cook evenly. I can't use most chemistry solutions to this, such as magnetic rods spun by a second magnet below attached to a motor, because the heat would damage any magnet involved. In addition, many foods are acid and would absorb an excessive amount of iron.
I can, however, use the industrial solution of a rod attached to large "wings," and rotate the rod by small motor. I know that this can be made not to melt or dissolve in the food, because "wings" exist that can survive being plunged into molten metal. Stirring would be done by yanking the device down into the pot. A non-corrosive metal should be used, or at least one with favorable nutritional properties.
Ovens should have a temperature probe that it can insert into the food and read. It could display this on the front of the oven, for the chef's convenience, so that it is no longer necessary to open the oven to see if the food is ready. Also, it would help if they could automatically turn over some foods, such as meats, say with a fork-on-a-jointed-rod that could be stabbed in, and torqued to deftly turn the food over. This would, again, be controllable from outside the oven, or, for greater automation, computer signal.
Most chefs enjoy distributing and laying out the food, but automation is again possible. A turkey-baster like device could collect fixed portions of soup or other liquid foods, large meat-and-vegetable portions could be cut with knives and placed on a plate with a tong-like device, and semisolid foods such as mashed potatoes can be automatically scooped.
A cook's least favorite part of the meal is cleaning up afterwards. Most foods leave behind residues of food on everything they touch, and should this residue remain untouched, it would rot and stink up the whole kitchen. In the bad old days, one would have to get a tub of water and soap and scrub the food off with a cloth or brush. Sinks mildly improved things, and dishwashers majorly improved things. Restaurants even have industrial dishwashers that can continuously load plates, wash them, and unload the plates for the incoming customers. (Most restaurants do not need to run them perpetually, but they have that ability if needed.) My own dishwasher is terrible, requiring the user to do 99% of the washing before finishing the job, and would literally cook the food onto the plate if given a dirty one directly. I will replace it sometime in the foreseeable future with a more recent design (which doesn't do that), but what can be done about all the dirty pots, pans, and other things that can't fit in the dishwasher?
I could have a cleaning robot that, on signal, comes out of a hiding place, scrubs all unused food from the utensils, vacuums the debris into a holding chamber, and gives a quick wash, soap, rinse, and dry. It would then place the utensil back into place, dispose of the dirty liquids in the sink, and return to storage. I imagine it being spider-shaped, with many legs for stability, several strong manipulators so that it can pick up heavy pots, scrubbing arms with attached bristles, a soap dispenser, a vacuum tube, and a chemical "nose" trained to recognize scents of common cooked foods. It would seek to the source of "cooked food," lift the source with the manipulators, scrub on all sides with the scrubbers, vacuuming each surface before turning. (Although if it does spill anything, there are four models of mopping robots on the market.) It would then apply a small amount of water, soap, scrub, more water, vacuum. It can rub a cloth on a utensil to dry it, then put it down. When it cannot find "cooked food," it should walk to the sink, which I assume can respond to a signal with another one, helping it find it, and eject the vacuum chamber's contents down the disposal. It should also be able to activate the water-flow and disposal by signal, stopping when the grinding reaches a certain tone. (The disposal sounds different when working empty and when grinding food.) It should then return to storage, where it can clean out the vacuum chamber with a wash or something, refill the water and soap, and possibly have the pads and cloth changed.
A somewhat larger robot spider could collect plates, and place them in the dishwasher. The dishwasher could be automatically run at certain times.
If all of these are computer controllable, one is now never too tired to cook, because now one can have preprogrammed recipes made for you with no effort on your part. Chefs that enjoy cooking can have their least favorite parts automated and manually do the rest.
The market for pre-packed food, (Better known as "TV Dinners" because they were invented when TV was new and therefore anything related was clearly a must-have thing made of pure awesomeness), would now be limited to people who genuinely like the way it tastes, and not the no-time-to-cook people or I-don't-know-how people that buy it now.
I also predict many interfaces for this, using a front end and a back end. The back end would actually direct the machines according to prepared instructions. The front end would have a nice user interface familiar to the user, and would list choices. There would be many front ends. A windows user unfamiliar with computers would have a DINNER icon on their desktop that they would double click, and it would provide a list of buttons with large pictures of the food. They would click the one that interested them. An adventurous UNIX user's front end would be a command-line script with a "-random" option that selected a random cuisine, which they would run daily from cron at maybe 5pm daily so that they could sit down to a new dinner every night by 6pm. (cron is a UNIX program that allows you to run programs at certain times, such as "6pm every day," or "every saturday at 12pm," or even "once a minute.")