Mix first 3 ingredients in small bowl. Season with salt and pepper. Spoon onto plastic wrap; roll into cylinder. Cover; chill at least 3 hours or overnight. Melt 2 tablespoons chili butter in heavy large pot over medium heat. Add onions; saute until deep golden brown, about 25 minutes. (Can be made 1 day ahead; cover and chill.) Steam potatoes until tender. Cool. Melt 3 tablespoons chili butter in heavy medium skillet over medium heat. Add potatoes; saute until golden brown, about 8 minutes. Mix onions and parsley into potatoes. Season with salt and pepper. Sprinkle steaks with salt and pepper. Brush 2 heavy large skillets with oil; heat over high heat. Add 2 steaks to each skillet; cook to desired doneness, about 6 minutes per side for medium rare. Rewarm potato mixture. Spoon onto plates. Top with steaks. Slice remaining chili butter; arrange atop steaks.