Mix the soy sauce and grated ginger. Add the slices of turkey.
Peel and wash and slice the potatoes thinly.
Sieve the flours together with the baking powder. Whisk in the chilled water to make a single cream consistency, then add the vinegar and place into the fridge and leave to stand for 30 minutes.
Heat the oil in a deep fat fryer (alternatively a deep sided pan).
Lay a slice of potato on a chopping board. Lay a slice of turkey on the potato, sandwich a second piece of potato on top. Repeat with each slice of turkey. Dust each "cake" with flour to coat, then dip into the batter and lower carefully into the oil and fry for 6 - 8 minutes.
Meanwhile melt 2oz butter and add the shallot and sweat, do not colour. Add the peas, mint, vinegar and water and cook for 3 minutes. Season and take half of the peas out, then crush the rest with a potato masher. Put the rest of the peas back in and check seasoning. When the cakes are cooked take out, drain and serve on the peas.