1. Heat oil in a large skillet until hot; add onions. Sauté 10 minutes or until golden brown, stirring occasionally.
2. Add chili de arbol, bay leaves, and thyme; cook 1 minute. Add white wine, and cook until reduced by half.
3. Add fish stock. Bring mixture to a boil; cook 25 minutes or until liquid has almost evaporated. Add butter to pan, stirring until melted.