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.
Remove from the heat, drain and run cold water all over them before draining again. This will stop them cooking anymore.
Put the potatoes carefully into the freezer bag or lidded container.
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.
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.
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
Place the skewered potatoes on the grill and cook for around 25 to 30 minutes, turning frequently.
Once golden brown all over, very soft and slightly charred, remove from the grill and serve.
To prep aheadYou can prep the potatoes up to 24 hours ahead of time. Parboil them and place in a bag or lidded container with the other ingredients, then refrigerate. Thread onto skewers and cook when needed.Success tips
It's not easy to get potatoes tender and cooked through on the grill alone, so parboiling is essential and guarantees soft and creamy insides.
Don't overcook the potatoes when parboiling or they will break when threading onto the skewers or when turning them on the grill.
Choose the smallest baby potatoes you can because they tend to be sweeter and more delicious once they are grilled.
Use potatoes that are all roughly the same size so they cook evenly.
Season generously. Salt enhances the flavour of potatoes so much.
Be generous with time and don't cook them too high. The longer you can keep them cooking on the grill the sweeter and more delicious they get.
Reheating leftoversLeftovers will keep for up to 5 days in the fridge and reheat perfectly either on the grill for about 10 minutes, in the oven on 350 °F for about 15 minutes or in a skillet, and can be served with any meal, whether it's cooked inside or out.