They both fell silent until he stirred in the last ingredient, counted the precise number of clockwise and counterclockwise turns of the wooden spoon, and set the mixture to simmering.  An hourglass levitated near the stove, the grains of sand ticking off the exact length of time before bottling, and Harry relaxed.  The hard part was done.  Now all he needed to do was let it sit on the low heat for a week, then bottle it up when the timer cried.