In a large saucepan over medium high heat add the oil and onion then sauté until softened.
Add the garlic and stir until fragrant; about 30 seconds.
Add the stock, split peas, diced carrot, diced potatoes, soy sauce, basil, black pepper, parsley flakes, ground sage, salt and bay leaves. Stir well to combine.
Add the smoked turkey legs and enough water to cover the peas and meaty part of the turkey legs by about 3cm.
Bring to the boil then reduce heat and simmer covered until the peas have softened; about 45 minutes. Check from time to time to ensure the water level is still above the peas. If not add a little more water.
Remove the turkey legs and the bay leaves. Discard the bay leaves. When the legs have cooled enough to handle; about 10 minutes. Remove the skin and bones from the turkey legs then shred or dice the meat into tiny pieces. Set aside.
Using an immersion blender, blend the soup to your desired consistency. Alternately you can use a food processor or blender.
Add the turkey meat back to the soup and stir to combine. Serve hot.