What do you gain by frying onions in bulk and freezing them?

The gain is being freed from doing the same step over and over. A great many dishes in our kitchen start with frying onions; if you do that once and freeze it in meal-sized pieces, on later evenings you enter the pot after that step. You have stocked not the whole preparation but only the common beginning.

Why this step in particular?

What pays off most in bulk preparation is what is repeated most. Vegetable dishes, dishes with ground meat, legumes, soup, stuffing mixtures; the first move in all of them is the same. Multiplying a finished dish obliges you to eat that dish, while multiplying the beginning leaves the evening's decision free.

The same logic holds for a base with tomato paste added to the onions. You prepare only the base; you decide that evening what dish the base will turn into. That is the clearest difference between this and a ready meal waiting in the freezer.

Why is cooling after frying a separate step?

Hot food is not put straight into the chiller. If a cooked dish will not be served straight away, it is cooled under suitable conditions and put in the fridge within two hours at most; a dish cooked in a large quantity is spread into shallow containers no deeper than ten centimeters and cooled quickly.

The thresholds the guideline gives make this step concrete: the temperature is to be brought from 60 °C to 37 °C in at most two hours, and from 37 °C to 4 °C in at most four hours. Spreading the base coming out of the pan onto a wide tray in a thin layer speeds that descent by itself. Not leaving a cooked dish on the counter or on the stove for more than two hours falls under the same heading.

The easiest way to shorten the base's cooling time is to move it onto a wide surface as soon as the frying is done. A hot mixture left in a deep container does not cool through the middle for a long time; the same amount spread onto a wide tray comes down clearly faster.

How is it portioned and packed?

Freeze the cooled base divided into meal-sized pieces rather than as one block. The guideline says foods to be frozen should be divided into portions according to the per-meal need, packed so that no air gets in, and kept in closed containers suitable for freezing. Since a purée-like mixture expands as it freezes, do not fill the container to the brim.

Write the type and the date of freezing on the package; that is what the guideline separately asks for foods frozen at home. Freezing it in an ice cube tray and then putting the cubes together into a bag is a practical route that makes taking out single pieces easier. The freezer setting should be at -18 °C or below; that is the value the regulation on quick-frozen foods defines for the product.

How does it go into a dish?

The base is already cooked and goes straight into a heated pot; there is no need to leave it standing at room temperature. The guideline says frozen foods should not be thawed at room temperature and, if thawing is needed, should be thawed in the fridge. If you want to thaw it in advance, that is the right place.

What you add on top is that evening's decision: legumes, vegetables, ground meat, or only water and spice. Because the beginning is fixed, the decision left for the evening gets smaller; the question "what should I cook" turns into "what should I turn this base into".

The method has its limit too: the more crowded the base, the less flexible it is. A mixture with spices, stock or vegetables added is no longer a beginning but half a dish. Keeping the base plain is what makes it suit more dishes.

What can you do today?

The next time you fry onions, put an extra layer of onion into the pan and move the extra into a separate container. Do the cooling on a shallow tray, and do not stack the containers. Keep the first attempt to two portions; you can raise the amount once you have seen that it works.