To make the keftedes, peel the potatoes and coarsely grate them into a colander over a large mixing bowl. Squeeze the grated potato to get rid of the liquid and starch, then leave to one side while you get the rest of the ingredients ready, reserving the liquid in the bowl underneath.
Mix the onion, parsley, mince (ground pork), egg, baking powder, cinnamon, mint, white pepper and a generous few pinches of salt in a large bowl. Squeeze small handfuls of the grated potato, to really extract all the moisture, and add to the pork mixture. Keep going until it is all used. Gently discard the liquid from the bowl that was under the colander and you’ll see a starchy sediment at the bottom. Spoon this in also.
Mix everything together well and add 60g (2 oz) of the breadcrumbs. Bring it all together and see how it feels – this might be enough breadcrumbs, or you might feel like it needs a little more. Don’t add too many, however, or it will dry out. Pat the mixture down, lay the slices of bread on top, and place the bowl in the fridge to rest for 1 hour. The bread will absorb any excess moisture.
When the mixture is ready, place the oil in a large saucepan and place on a medium heat. Cut a small cube of potato or bread and put it into the oil. When it starts to sizzle and turn golden, the oil is ready to use.
Use a tablespoon to scoop the mixture and with slightly wet hands, mould into an oblong or round shape. Fry them in batches of 5 or 6, so the pan isn’t overcrowded, for around 6-8 minutes, depending on their size. They should be golden and cooked through.
Transfer to kitchen paper to drain off the excess oil, and keep going until all the mixture is used up. Serve straight away, or at room temperature.
For the yoghurt dip
To make the yoghurt dip, mix the ingredients together in a small bowl.