Step 1

Heat oil in a small skillet over medium. Cook onion, garlic, and thyme, stirring occasionally, until onion is deep golden brown and very soft, 35–40 minutes. Discard thyme and let cool.

Step 2

Mix caramelized onions, shallot, sour cream, chives, and lemon juice in a medium bowl; season with salt and pepper. Let sit 30 minutes to let flavors meld. Serve with potato chips for dipping.

Step 3

Do Ahead: Dip can be made 1 day ahead; cover and chill.