Heat the butter in a frying pan and cook the onions for a couple of minutes, until slightly soft and translucent. Transfer to a bowl, and add the mashed potatoes, kale or cabbage, sweetcorn, cooked turkey and salt and pepper. Mix well.
Add the olive oil and a few dry breadcrumbs to form a firm, but not stiff mixture. Form into 4 balls, flatten slightly, and dust with flour.
Brush egg on both flat sides of the cakes and sprinkle with breadcrumbs, pat down lightly.
To make the dressing whisk the ingredients together with a little salt and pepper. If the mixture is too thick add a touch of milk.
To cook the cakes, heat a little vegetable oil in a frying pan and fry on both sides for 3 minutes. Place a few salad leaves onto a warm plate, top with a cake and a spoonful of yoghurt dressing.
© Phil Vickery