In a soup pot, cook bacon until crispy, remove to paper towels to drain, and reserve for garnish. Add oil and flour to pot and cook for 3 minutes, stirring. Add leeks and cook 3 minutes. and add stock. Bring to a boil, reduce heat and simmer for 30 minutes. Add peas and cook 5 minutes. Using an immersion blender, puree soup in the pot; or pour soup into a food processor or blender, process until smooth and return to pot. Stir in cream and adjust season, to taste, with salt and pepper. Ladle soup into a warm tureen and serve garnished with and chives.