Wash the peas to remove dust. Spread on a towel and remove any debris. Heat a heavy bottomed soup pot over medium high heat. Add oil and heat, add onion, garlic, celery and carrots. Saute until soft, about 5 minutes. Add smoked turkey, peas, salt and stock. Bring to a boil. Reduce the heat to simmer, and cook, partially covered, until peas are tender, 45 to 60 minutes. Remove turkey from pot and remove meat from the bones. Finely shred meat and put back into the pot. Stir in sage, lemon zest and cayenne and cook for another 5 minutes. Taste and adjust for seasoning with salt and pepper. Ladle pea puree into serving bowls. Garnish with chopped parsley and serve immediately.