8 small–medium potatoes, each one approx. 75g/2¾oz, scrubbed (ideally, all-rounders or floury potatoes)
½ tsp dried thyme, rosemary or mixed herbs
½ tsp coarsely ground black pepper
3 tbsp sunflower, vegetable or olive oil, plus extra for greasing
½ tsp flaked sea salt
small knob of butter, approx. 15g/½oz (optional)