I generalized it into THREE steps in total.
1. simmer potatoes at 65 degC for 30mins, then cool in a freezer for at least an hour.
2. fry in warm oil at 130degC for 5mins, then cool in a freezer for at least an hour.
3. fry in hot oil at 190degC for 7 mins, serve.
After executing the task. I came to realized that the preparation and procedures are quite complicated and required lots of tweaking. Furthermore, without the thermometer cooking is really guesstimation or what the Singapore people would say : Agaklogic.
If you asked me is it worth the effort? Yes, if time allows. Yes, if this process can be automated. Yes, if the products can be prefabricated. Sounds like an engineering challenge? heheheheehe
1. wash and the cut the potatoes into thick cuts. wash under running water for few minutes to remove the starch.
2. Bring a pot of water to boil, simmer the potato chips at 65degC to 75degC. Potatoes are more forgiving and less temperamental. No pun intended! If the water is getting hotter, turn off the gas knob for a while. Use a thermometer. Mine is capable of -50degC to 300degC. It cost me £19.90 from Maplin, but totally worth and the first equipment to be purchased to pursue molecular gastronomy.
The potatoes are simmering at 68.8 degC
3. Rinse the potato from excess water.
4. Using an oil splatter guard, I fan out the chips on it. Such that each piece of chips have a chance to remove the moisture while sitting pretty in the freezer.
5. There might be excess water droplets.
6. Freeze it over night. This is how it looked like in the morning.
7. Heat a pot of oil to 130degC. Some cook book will say fill with X amount of oil and etc. Now the tricky bit. The amount of oil should be sufficient to cover the chips in it. So, fry in small batches. The next tricky bit. If you put too much oil and overly guesstimate the volume of potatoes going into it and there will an overflow of oil. If you are using a naked flame for cooking, good luck with the fire extinguisher. If not, huge mess to clean up. Word of caution: If scalded, use cold running water to remove the heat on the affected area. This will prevent the heat from penetrating the dermis, causing further injuries and will take even longer to heal.
Oil is at 133.4degC
8. The objective is to heat the chips at 130degC consistently. If the chips are at room temperature, the oil temperature should not be higher then the ideal temperature. If the chips are cook from chilled state, significant heat loss will occur. It will take longer then the stated ideal cooking time and hence oil soaked chips. Maybe some heat exchange expert can explain the thermodynamics of the chilled chips entering hot oil and the time constant needed to reach the desired temperature?
Oil is at 117.1degC with chips in it.
9. It took about 4mins to reach the ideal heat of 130degC. In other words, the chips are spending longer then required time (about 8minutes in total) in the oil.
Oil is at 130.3degC after 4 mins of cooking on high heat
10. The chips soaked in warm oil will look nicer then the uncooked ones. Excess oil is drained on kitchen towel. It can be stored in the freezer for later use.
comparison of chips
close up of chips cooked at 130degC
11. Move the drained chips to the freezer and freeze for at least an hour.
12. When ready to cook the chips, heat the oil to the desired temperature of 190degC. Since I am cooking from a frozen state, I heated it to 220degC to preempt sudden temperature drop. Once the temperature is at the desired state, turn the gas knob to maintain the temperature.
After the frozen chips went it, the temperature drop to 203degC.
13. My chips looked orangey, nothing close to the golden brown colour i saw from Heston's show on BBC4. My speculation is the higher temperature I set at step 12.
Crispy exterior and a mash potato center at the same time.
14. Roast chicken and chips. The greens are for garnishing only.
15. Size does matters. I mean the cut of the chips for cooking with this method.
16. Washing is such a chore. The massive amount of grease stained plates, sieves, pots, and etc to wash is a nightmare.