In a large nonstick skillet, melt the butter over medium heat and add the olive oil. Add the onions and stir until they are well coated in the butter and olive oil. Move the onions around so they are in a single layer in the pan. Cook for about 10 minutes, stirring occasionally.
Reduce the heat to medium low. Season with salt to draw out the moisture and add a little sugar to enhance the sweet flavor. Add the fresh thyme. You want to cook the onions slow and low so they have a chance to caramelize. The onions will shrink down and get tender and juicy. This will take about 30 minutes to an hour. Make sure you stir the onions every few minutes or so so they don't burn. You don't want to stir them too often though, or they won't caramelize and brown. You want them to brown, but not burn. Just make sure you look at them every few minutes and give them a quick stir if they need it.
If the onions start to dry out, you can add a little water or broth to the pan.
In the last ten minutes, stir in the balsamic vinegar to give the onions flavor. Turn off the heat and carefully transfer the onions to a cutting board. Let the onions cool for a few minutes and then roughly chop them with a sharp knife.
In a medium bowl, combine the caramelized onions, sour cream (Greek yogurt), garlic powder, salt, and pepper. Stir until smooth and onions are mixed in well.
Serve with Kettle Brand chips.
Notes
Keep the dip covered in the refrigerator for up to 4 days. It can be made in advance.