In the skillet, heat the oil over medium heat and add the garlic, stirring for about 30 seconds.
Add the chopped peppers and cook for about 1 minute, then add the balsamic vinegar and cook over moderately low heat, stirring, until dry, about 12 minutes.
Transfer to a bowl to cool. Stir in the sour cream and basil and season with salt and pepper. Cover and refrigerate until chilled.
Instead of using jarred peppers, you can roast your own. Roast the peppers over a gas flame or under the broiler until charred all over. Put them in a plastic bag and let steam for 20 minutes. Remove the skins, cores, and seeds. Pat the peppers dry and chop.To use dried basil, cook it with the peppers and vinegar.