The recipe for Potato Puree in "Modernist Cooking at Home" calls for precooking the potatoes in water at 65 degrees Celsius for 35 minutes. The bag should hold 500 g potatoes and 1 liter water. Since the recipe says to scale the water at 200% this means that if I am to use 1 kg of potates I need 4 liter of water.
However, trying to do this for only 35 minutes did not give a satisfactory result. Looking back, this is not surprising since the added size of the bag means it needs more time in the sous vide.
What is the right way to scale up the recepie? Should I use two bags? If that is the case, the scaling factor of the water makes little sense. How about 750 grams of potatoes, or 1.5 kg of potatoes?