Slice 3 large yellow onions into thin ⅛-inch strips using a sharp chef's knife, ensuring uniform thickness so they caramelize evenly without burning.
3 large yellow onions
Melt 2 tablespoons butter in a cast iron skillet or heavy-bottomed pan over medium-low heat. Add the sliced onions and stir to coat them in butter. Spread onions into an even layer.
2 tablespoons butter, 3 large yellow onions
Cook onions on medium-low heat for 30 to 40 minutes, stirring every 5 minutes to prevent sticking and ensure even browning. If onions darken too fast, lower the heat slightly. Add 1 teaspoon salt during the last 5 minutes of cooking.
3 large yellow onions, 1 teaspoon salt
Cool the caramelized onions to room temperature. Then mix them with 1½ cups sour cream, ½ cup mayonnaise, 1 tablespoon Worcestershire sauce, and ½ teaspoon black pepper in a mixing bowl. Gently fold with a spatula until combined evenly.
3 large yellow onions, 1.5 cups sour cream, 0.5 cup mayonnaise, 1 tablespoon Worcestershire sauce, 0.5 teaspoon black pepper
Cover and refrigerate the dip for at least 2 hours before serving to allow flavors to meld. Just before serving, top with 2 tablespoons chopped fresh chives and serve with chips or vegetables.
2 tablespoons fresh chives
