Peel the potatoes and cut into small chunks. Cook with the carrot in a pan of boiling water until tender. Drain, move the carrots to one side, and mash one-quarter of the potatoes, leaving the rest in chunks.
Heat the oil in a large pan, add the onion and fry over a low for 5 minutes. Stir in the carrot, celery and turkey and fry for a further 5 minutes, stirring frequently.
Mix the flour with a little of the stock until smooth and add to the pan with the rest of the stock and the mashed potatoes. Stir over the heat until smooth and thickened, then simmer for 5 minutes.
Stir in the sweetcorn, peas, double cream, potato chunks and seasoning and simmer for a further 5 minutes. Serve hot, garnished with the chopped parsley