Step 1

Preheat oven to 180°C/350°F. Brush skillet base and sides with a little olive oil.

Step 2

Slice potatoes: Slice potatoes 3-4mm thick. A mandoline will make short work of this.

Step 3

Toss: Place in large bowl, pour in all butter plus 1 tbsp olive oil, rosemary, salt and pepper. Toss well with hands, separating the slices so they are all coated with oil.

Step 4

Layer in skillet: Layer potato in skillet in a circular pattern, overlapping the slices. (See post for details)

Step 5

Bake covered 30 minutes: Cover with foil, bake for 30 minutes until potato is quite soft (almost fully cooked).

Step 6

Brush with oil: Remove from oven, turn up to 220°C/430°F (200°C fan). Remove foil, brush potato with remaining 1 tbsp oil.

Step 7

Bake uncovered 20 minutes: Bake 20 minutes until tops are golden and slightly crisp, and potato is cooked through (check with a knife or skewer).

Step 8

Serve: Scatter with more rosemary leaves, a whole sprig of rosemary and pinch of sea salt flakes if desired. Serve immediately! Sweet potato loses crispiness as it cools.