Set out your block of cream cheese so that it is soft when you need to beat it later.
Caramelize the onions: Thinly slice the 3 onions. Thin slices caramelize more evenly than big ol pieces!*
Set a 12-inch high sided pan over medium heat. Melt 3 tablespoons butter, then add all the onions. Sprinkle with 2 teaspoons kosher salt, 1 tablespoon sugar, and 1/8 teaspoon cayenne pepper. The cayenne is for flavor and not heat, if you like things a lil spicy, add 1/4 teaspoon!
Saute the onions over medium heat for about 5 minutes, stirring occasionally. Lower the heat to medium low, and settle in for the long haul. Onions take about 40-50 minutes to caramelize fully.
Eventually, after 10-15 minutes, the bottom of the pan will get dry and the onions will start sticking to the pan. At this point, deglaze the pan by adding 3 tablespoons white wine vinegar and using a wooden spoon to scrape up all the browned bits on the bottom of the pan.
Add 1 teaspoon beef base and stir it all together. Keep sauteing until you have reached the 40-50 minute mark. If the pan gets very dry and the onions start to blacken on the edges, add 1 tablespoon water and stir. Repeat this process as often as necessary. At the end, your onions should be a deep brown caramel color, with no white parts, and not blackened. (not too much, anyway.)
Remove the onions from the heat and let cool for a while. When you can handle them, scrape them onto a cutting board and chop into bite-size pieces.*
Make the dip: Meanwhile, in a medium bowl, add 8 ounces softened cream cheese. Beat with a hand mixer until it is smooth and creamy, and there are no lumps.
Add 1 and 1/2 cups sour cream, 1 small clove of minced garlic (about 1 teaspoon), 1 teaspoon Worcestershire sauce, and 1 teaspoon lemon juice. Continue beating until it's all mixed together. Give it a taste and add salt and pepper to taste!
Use a rubber spatula to fold in the cooled and chopped caramelized onions. Transfer to a serving dish and sprinkle with chopped chives (or green onions are good too, thinly sliced).
Serve right away with potato chips! I like the crinkle cut potato chips, I feel like they are sturdier and hold up better for dipping.
Store the dip in a covered container in the fridge. It will keep for a couple weeks! (Ask me how I know 😂) This is a GREAT make ahead appetizer, the flavors just get better with time.
Notes
*You can chop your onions into a normal dice before cooking, if you wish. I'm always crying a thousand tears by this point and want to get them in the pan as fast as possible, so I just slice and go! We don't want long stringy onions in our dip; I always take the step to chop up the onions after they have caramelized. But if you are not a crier, you can do the full dice before cooking, if that's more convenient!