Thoroughly wash the potatoes and slice, leaving the skins on. Place in a bowl of cold water.
Crumble the feta into a bowl. Wash the thyme, shake dry, pick off the leaves and add to the feta.
Grate the lemon zest and add to the feta.
Season the feta mix with vinegar, olive oil, pepper and nutmeg to taste.
Heat a deep-fat fryer or deep pan half-filled with oil to 170°C. Remove the potato slices from the water, pat dry and fry in batches for 3 minutes in the hot oil. Remove, allow to cool then refry until golden brown. Drain, season with salt and serve with the marinated feta.