Retained heat cooking is an ancient technique. It was practised in two different ways:

1. Using heavy stoneware – Food was brought to boil in heavy stoneware. The vessel absorbed and retained a lot of heat and continued to cook even when taken off the heat source.

2. Using insulated containers – Food was brought to a boil in a pot, removed from heat and placed in an insulated container. The insulation prevented heat loss. The contents continue to cook in the retained heat.

These were the slow cookers of the ancient world. There are numerous benefits to cooking this way:

1. No threat of burning/ clumping

2. No threat of overcooking

3. Fuel consumption is greatly minimised

4. Hot, ready to eat food is available after many hours

5. No need for constant supervision

6. Multiple dishes can continue to ‘cook’ together and can be all served at once.

This same principle is followed in the present day Vacuum flask recipes.

The first benefit of no burning/ clumping was what we were interested in, when we were trying to cook Kesari/ Sooji Halwa. The traditional method of cooking kesari has major problems for an unskilled cook.

1. It requires continuous supervision

2. It is prone to clumping if you don’t stir well

3. It can easily get overcooked and become gummy if you are not careful enough.

Let’s take a look at the traditional recipe :

Kesari : The traditional version

1. Boil 2 cups of water. Add 1/2C roasted rava.

2. Mix well till all the water is absorbed by the rava.

3. Close the vessel with a lid and cook for 3-4 minutes. Stir once a while.

4. After the rava is cooked well,add 1C sugar, 1/4C ghee.Mix well.

5. Keep stirring and mixing till it becomes thick and leaves the sides of pan completely.

Steps 3,4 & 5 are tricky as they are very subjective. When we tried to OPOS kesari, we tried out nearly 27 versions, and proposed half a dozen recipes. None worked for all. Clumping/ burning always happened. The key breakthrough came when we realised that clumping is caused by uneven heating. No clumping can happen when there is no temperature difference across the pot. We tried double boiling rava in a water bath to make this possible, but the bottom layer clumped up.This is when we stumbled upon retained heat cooking. The key advantage of retained heat cooking is that the whole pot is at exactly the same temperature. There is a total lack of uneven heating. This completely eliminates any need to stir.

All we had to do was to estimate the amount of liquid needed to get the consistency we liked. We estimated it varies from twice the volume of rava to nearly seven times. We realised retained heat is the way to OPOS this recipe. The trick was to boil just enough water that is sufficient enough to both cook the grits and get completely absorbed. As raw grits cannot cook completely in retained heat, the recipe was tweaked to add double roasted grits, which are already mostly cooked. Fortunately, double roasted grits are industrially processed and were commercially available.

The following recipe was proposed:

OPOS Kesari

In a 2L pot, add 1/4C sugar, 3tsp ghee, 1C water. Cook on high for 1 whistle. Switch off heat. Release pressure. Mix in 1/4C double roasted rava. Keep closed for 20 mins.

It was soon extended with fruit purees and opened up the template for fruit based kesaris. These recipes struck a chord with members and validations started pouring in. Kesari has special significance in many households and members rushed to try the OPOS version. We soon clocked over 100 independent validations. The same technique was extended with roasted vermicelli. Then the salty version of kesari – Upma/ Rava kichidi (grits based savoury porridges), was unlocked.

We then extended the same concept to pressed rice (poha). This recipe opened the door for converting any pressurebaked curry into a full meal. The same recipe was extended to make Bread upma and Tawa Pulao. By mixing in starch with pressurebaked vegetables, we found we can instantly convert any dry curry into a full meal.

We then used the retained heat technique to ‘cook’ gluten-free flours.

Kneading gluten free flours is not possible as they do not have a binder. Traditionally, they were mixed and kneaded with boiling water. The heat partially cooks the flour into sticky starch, which can then be kneaded and shaped. After kneading, they are then turned into flatbreads, dumplings (ammini kozhukattai/ modak/ mudde), flatbreads ( Akki roti, bejad ki roti,..), or extruded into idiappam (string hoppers).

Retained heat cooking is also employed in some pasta recipes. In no water cooking of pasta, when pressure is released, the pasta is not fully cooked. It is then mixed well to declump it and then left to cook in the retained heat for 5 – 10 minutes.

In recipes that call for simmering with yogurt/ milk/ coconut milk, we face a risk of splitting. In such cases, we mix in dairy products after cooking is over and they cook in retained heat, with no risk of splitting.

In recipes like Aviyal & Kurukku kaalan, the coconut-chilli paste is sometimes mixed in after the curry is cooked, and left to cook in the retained heat.

In Pasta carbonara, Egg drop soup, Shakshouka and other recipes using eggs, eggs are cracked into the simmering curry and left to cook in retained heat, with no further heating.

Retained heat cooking has emerged as a core technique for cooking wheat grits, pressed rice, vermicelli, eggs & non- gluten flours.

Scaling up:

Retained heat cooking scales up seamlessly. We have cooked over 7Kg kesari for charity events by scaling up the same recipe. Members who run restaurants have cooked up even larger batches successfully.