2Heat a large saucepan or Dutch oven over medium heat for 1 minute. Add the butter, and when it foams, add the diced and sliced onions, thyme, 2 teaspoons salt, and the white pepper. Turn the heat down to medium-low, and cook the onions gently, for about 10 minutes, stirring often. They should soften and wilt but not be allowed to color at all.