Thinly slice your onions. Mince the clove of garlic and fresh tyme.
Set a large cast-iron skillet or large sauté pan over medium heat and add the olive oil and butter.
Add the sliced onions and stir them well to coat them in the butter. Spread them out into an even layer in the pan and stir every 2-3 minutes.
After the onions have softened and start to develop color, add the minced garlic and fresh thyme.
Cook the onions until they are soft and a deep golden brown. Once the onions are cooked completely, add the dry sherry, beef stock, onion powder, salt, and pepper. Scrape up the caramelized bits from the bottom of the pan.
Reduce the liquid until it's almost completely gone.
Turn off the heat and let the onions cool for at least 10 minutes.
Transfer the cooled onions to a small food processor and pulse until they are broken up into fine pieces. You can also do this by chopping them on a cutting board.
Lastly, in a large mixing bowl, combine the cooked onions with the sour cream and cream cheese. Stir until the mixture is well combined and check the taste for seasoning. Add salt or pepper if needed.
This dip is best cooked a day ahead. Refrigerate the onion dip in an airtight container overnight. The next day, take the dip out of the refrigerator 30 minutes before serving.
Serve the dip in a chip and dip bowl set with plain potato chips with ridges or cut veggies such as carrots, celery, and bell pepper.