Directions

• Melt butter with oil in heavy large pot over medium heat.
• Add onions, cover and cook until lightly colored, stirring occasionally, about 45 minutes.
• Add wine and bring to boil, scraping up any browned bits.
• Cook 5 minutes.
• Add browned bits.
• Cook 5 minutes. Add stock and bring to simmer.
• Preheat broiler.
• Sprinkle with grated Gruyere cheese.
• Serve immediately.