In a large pan, heat oil on medium-high heat and add onion, garlic cloves and thyme. Cook for 10-15 minutes, stirring often, until onions have softened and turned golden in color. Remove from heat and let cool. Remove thyme sprigs.
Once cooled, combine onion mixture, sour cream, chives, and lemon juice in a large bowl. Season to taste with salt and pepper. Let chill before serving and enjoy!