Whisk the sour cream, minced cilantro, and lime juice together in a small bowl. Season with salt and pepper to taste, then cover and refrigerate until the soup is ready.

Position an oven rack 3 inches from the broiler element and heat the broiler. Arrange half of the peppers skin-side up on a foil-lined baking sheet and broil until the skin is charred and puffed but the flesh remains firm, 8 to 10 minutes, rotating the sheet halfway through. Transfer the hot peppers to a bowl, cover with plastic wrap, and let steam until the skins peel off easily, about 10 to 15 minutes. Repeat this process with the remaining peppers, then peel and coarsely chop.

Combine the oil and garlic in a Dutch oven over low heat. Cook, stirring constantly, until the garlic becomes foamy, sticky, and straw-colored, 8 to 10 minutes. Add the onion, increase the heat to medium, and cook until softened and translucent, 5 to 7 minutes.

Stir in the cumin and paprika and cook until fragrant. Add the tomato paste and flour, stirring for 1 minute to cook out the raw flour taste. Gradually whisk in the vegetable broth, making sure to smooth out any lumps. Stir in the bay leaf and chopped roasted peppers, bring to a simmer, and cook until the peppers are very tender, 5 to 7 minutes.

Discard the bay leaf. Puree the soup in a blender in batches until completely smooth, about 1 to 2 minutes per batch. Return the soup to a clean pot and stir in the half-and-half and sherry. If the soup is too thick, stir in additional broth until it reaches your desired consistency. Heat gently over low heat until hot, but do not let it boil. Stir in the chopped cilantro and season with salt and pepper. Serve hot, drizzling each bowl with the chilled cilantro cream.