Start by peeling the potatoes and cutting them into even chunks.
Place them in a large pot, cover with cold water, add the baking powder and mix.
Bring to a boil, I cooked mine for ~20 minutes total, until soft around the edges.
Drain them well and allow the steam to escape so the edges dry slightly.
Place a roasting tray in the oven with the olive oil and preheat to 230°C (450°F).
Once the tray is hot, carefully add the potatoes and toss to coat in the oil.
Roast for 40 minutes. After 15 minutes, flip them, then roast for another 25 minutes until golden and crisp.
While the potatoes are roasting, chop the rosemary very finely, add the olive oil, and mix well.
Take the tray out of the oven at the 40-minute mark, drizzle the rosemary oil over the potatoes and toss to coat.
Return the tray to the oven for the final 5–10 minutes until the edges are extra crispy.
Serve immediately while hot and crunchy.
