In a large skillet, melt 2 tablespoons of butter over low heat. Add 4 cups of diced sweet onions and cook slowly for 45 to 60 minutes, stirring occasionally.

Once the onions have caramelized, sprinkle in 1 tablespoon of brown sugar, 1 tablespoon of soy sauce, a dash of black pepper, and cayenne pepper if desired. Stir well and cook for another 10-15 minutes.

Remove the skillet from heat and let the caramelized onions cool to room temperature.

In a mixing bowl, beat together 8 ounces of softened cream cheese and 1/2 cup of mayonnaise until fluffy. Gradually fold in 1/4 to 1/2 cup of sour cream according to your taste.

Gently fold in the cooled caramelized onions and about 1/4 cup of finely chopped chives. Mix in buttermilk powder if using.

Cover the bowl with plastic wrap and refrigerate for at least 1 hour, or ideally overnight.

Before serving, stir the dip well and adjust seasoning with salt or pepper. Serve with chips, crackers, or as a spread.