Melt butter in a large nonstick skillet over medium-high heat; add onions, and cook, stirring occasionally, 20 minutes or until browned and tender. Sprinkle with 1/2 tsp. salt and 1/4 tsp. pepper. Remove from heat, and let stand 30 minutes.
Stir together onions, sour cream, and chives in a medium bowl. Stir in remaining 1/2 tsp. salt and remaining 1/4 tsp. pepper. Cover and chill 30 minutes or up to 2 days. Serve with potato chips.
Love, love, love this. Have made it several times for several gatherings the last 3 months and it's devoured. I could easily eat the whole thing with a spoon and no remorse. Taste even better the next day, if any is left.