Step 1

Put the potatoes into a large pan of cold water with 1 teaspoon of the salt. Bring to a boil and cook them until you can just stick a fork or knife into them with some resistance (about 10 minutes but this varies depending on the size). then remove from the heat and drain.

Step 2

Remove from the heat, drain and run cold water all over them before draining again. This will stop them cooking anymore.

Step 3

Put the potatoes carefully into the freezer bag or lidded container.

Step 4

Pour in the oil, rosemary, remaining salt and pepper then seal the bag/container and give it a good shake around to distribute the oil and herbs all over the potatoes.

Step 5

Leave to marinate in the fridge for as long as you can, but for at least 30 minutes. They can be prepared like this up to 24 hours in advance.

Step 6

When you are ready to cook the potatoes, remove them from the fridge and thread onto skewers. If using wooden skewers make sure you soak them in cold water for a while first so they don't burn on the grill

Step 7

Place the skewered potatoes on the grill and cook for around 25 to 30 minutes, turning frequently.

Step 8

Once golden brown all over, very soft and slightly charred, remove from the grill and serve.