How to Make It
Preheat broiler with oven rack 6 inches from heat. Line a rimmed baking sheet with aluminum foil. Cut bell peppers in half lengthwise, and remove stems, ribs, and seeds. Place pepper halves, cut sides down, on prepared baking sheet. Flatten peppers with the palm of your hand. Broil until very well charred, about 15 minutes, turning baking sheet after 10 minutes. Remove from oven, and cover with additional foil, sealing edges to retain heat. Let stand 15 minutes. Remove charred peel from pepper halves. Coarsely chop peppers.
Heat oil in a Dutch oven over medium. Add shallots, carrot, celery, and garlic; cook, stirring occasionally, until vegetables are tender, about 10 minutes. Add chopped peppers and stock; bring to a boil over high, and let simmer until flavors are melded, about 5 minutes. Remove from heat.
Scoop 5 cups of hot soup into a blender. Remove center piece of blender lid (to allow steam to escape); secure lid on blender, and place a clean towel over opening in lid. Process until smooth, about 1 1/2 minutes; transfer to a large bowl. Repeat process with remaining soup. Stir in sour cream, salt, black pepper, and red pepper until smooth. Chill at least 3 hours or overnight. Sprinkle each serving with pepitas and red pepper.