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1
Heat sugar in a 12-inch stainless-steel skillet (not non-stick; you won't be able to see the color change) over medium-high heat until completely melted and light brown, about 3 minutes.
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2
Immediately add onions; stir with wooden spoon (metal will cause caramel to seize and crystallize) until onions are coated in sugar.
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3
Add butter, baking soda, 1 teaspoon kosher salt, and a few grinds of black pepper.
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4
Toss to combine.
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5
Cook, shaking pan occasionally until onions release all their liquid and brown fond covers bottom of pan, 6 to 8 minutes.
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6
Add 2 tablespoons water and shake pan while scraping with wooden spoon to deglaze bottom of pan.
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7
Continue cooking, shaking occasionally until fond begins to accumulate again, 3 to 5 minutes.
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8
Repeat deglazing and cooking steps three more times until all the water has been used and onions are deep brown.
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9
Transfer to medium mixing bowl and allow to rest at room temperature for 5 minutes.
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10
Combine sour cream, mayonnaise, lemon juice, parmesan, and Worcestershire and whisk.
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11
Stir in onions.
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12
For smoother texture, run through blender or food processor.
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13
Chill in a sealed container for at least 1 hour and up to 5 days (flavor will improve with time).
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14
Spoon into a bowl, sprinkle with chives, and serve with chips.
