How to Make It
Set a large skillet over high heat. Add the spinach by the handful and stir to wilt. Cook just until all of the spinach has wilted, then transfer to a colander. Let cool slightly, then squeeze the spinach dry and coarsely chop it.
Heat 1 tablespoon of the olive oil in a small skillet. Add the scallions and serranos and cook over moderately high heat until softened, about 2 minutes. Transfer to a blender and add the wilted spinach, cilantro, sour cream, lime juice and the remaining 1/4 cup of olive oil. Blend to a smooth puree, scraping down the side occasionally. Transfer the dip to a bowl and season with salt and pepper. Serve chilled or at room temperature with a platter of the assorted vegetables.