Start by melting the unsalted butter in a large skillet over medium heat. Once it's melted and bubbly, toss in your finely chopped onions. Stir them often, allowing them to soften and caramelize. This usually takes about 15 to 20 minutes, but don’t rush it! You want those onions to turn a lovely golden-brown.

Once the onions are beautifully caramelized, sprinkle in the roasted garlic powder. This adds a wonderful depth to the flavor and complements the sweet onions. Stir it well for about a minute, until fragrant.

While the onions cool slightly, grab a mixing bowl. Add the cold cream cheese, mayonnaise, and sour cream. Use a hand mixer or whisk to blend these ingredients until they’re smooth and creamy. This helps you avoid lumps in your dip.

Now that your onion mixture has cooled a bit, fold it into the creamy base. Mix thoroughly, and incorporate the Worcestershire sauce, cayenne pepper, black pepper, and salt. Give it another good mix, tasting and adjusting the seasoning as you prefer.

Transfer your dip to a serving bowl and cover it. For the best flavor, let it chill in the refrigerator for at least an hour. This allows all the flavors to meld beautifully.

Just before serving, sprinkle the chopped fresh chives on top. Those bright green bits not only look appealing but also add a lovely fresh flavor against the rich dip. Don't forget to serve it up with your favorite dippers!