I just tried the recipe with excellent results. It seems to me that to be successful there must be water in the PC when you are done. If there isn‚’t, the bottom will have gotten much hotter than intended. At this point it is no longer a PC, but rather a stove top Dutch oven. All temperature control is lost, overheating anything that is inside, especially anything in contact with the bottom. When I open my PC the factory trivet is still under water, and I start with the recommended 2.5 cm. I don‚’t think that more water hurts anything except that it requires more energy to heat before it starts boiling.
I am amazed at how little heat is required to keep my PC at pressure. I start on a fast burner to get it to a boil, and then move it to the smallest burner in my stove. I find I have to turn that burner down almost to its smallest flame. For the first 10 or 20 minutes I tend the pot and make small adjustments to the flame so the pressure stabilized where I want it. From then on, I check it once and a while until the two hours is over at which time I turn the gas off. I return 10 or 15 minutes later and open it up after making sure the plunger on my PC is fully down.
The lower the flame, the less water is converted to steam. It seems to me that as long as the PC is at pressure, any additional energy is lost boiling water which has to escape to keep the pressure where it needs to be. The two hours this recipe requires is long, so the water used to make the steam that is lost to the outside needs to be anticipated. I could see some PCs needing more than the recommended 2.5 cm if they are not turned down enough.
