Remove casing from chorizo, if present. In a large, nonstick skillet, cook chorizo over medium-high heat until brown, using a spatula to break up the meat. Reserving drippings in skillet, use a slotted spoon to transfer chorizo to a plate lined with paper towels; set aside. To reserved drippings, add potatoes, onion, bell pepper and garlic. Sprinkle with salt and pepper. Cook over medium-high heat for 12 to 15 minutes or until potatoes are crisp on the outside, adding olive oil as necessary to avoid sticking. Stir in chorizo and reduce heat to medium-low. In a small skillet, melt butter over medium heat.