When the butter is melted, add the mountain of onions, a small pinch of sugar, a big pinch of salt, and a branch of fresh thyme, and stir it all well. Cook the onions over medium-low heat, stirring them occasionally. Add occasional sprinkles of water if the onions begin to stick. If they start to sizzle, lower the heat and cover the pot, then uncover it when the cooking has slowed. This will take forty-five minutes to an hour, and the whole mass will look soggy and unconvincing until right before the onions are done, at which point they melt completely into a golden jam and all of their sugars come out to toast.