Chiles: Put the poblanos over a gas flame, underneath the broiler, or on the grill and cook until they are blackened on all sides. Enclose them in a plastic or paper bag and let stand for at least ten minutes to steam. Peel and devein them, then cut into small pieces.

Dip: Preheat the oven to 350 degrees F. Butter an 8"-square glass baking dish.

In a heavy saucepan, melt the butter. Add the onion and cook until translucent, about four minutes. Add the poblano pieces and sauté for about 2 minutes. Let cool.

Put the artichoke hearts, cream cheese, mozzarella, sour cream and mayonnaise in a food processor and process until smooth. Add the onion-poblano mixture and pulse a couple times until combined, making sure to leave the mixture a little chunky. Season with salt and pepper.

Transfer the mixture to the prepared baking dish and bake until golden brown and melted, about 15 minutes.