Pre-heat the oven to between 200 and 220 C (400 to 425 F/Gas 6 to 7).
Cut 'slits' into each potato from end to end (starting at one end and working across). The slits are best cut thin - about 3 mm (⅛ inch) apart. Hold the potato firm and cut straight down into it (being careful of your fingers). Don't cut all the way through… Stop at about the three-quarter point. (see NOTES below for tips to help).
Once cut, place in a roasting tin and drizzle over a little olive oil.
Using your hands, rub the olive oil into the potato skins (so that they all have a covering) and place back into the pan, slit side up.
Season with a little salt and pepper and place in the oven.
Roast the potatoes for about 30 minutes before removing and adding additional seasoning, herbs and melting some of the butter or garlic butter over the tops. Be sure to coax some of the butter and garlic into the 'cracks'. If you are adding other toppings that require a little time in the oven, now is the time to pop them on. (But add any cheese about 15 to 20 minutes before the end of cooking).
Place the potatoes back into the oven and roast for a further 30 to 40 minutes or until crisp and golden.
When ready, remove from the oven and top with the remaining butter/garlic butter.
Serve and smile.
Note: nutritional information is an estimate & may vary according to portion size/ingredient variants.Optional 'tricks' to help in cutting Hasselback potatoes :
Place each baby potato in turn in the 'scoop' of a wooden spoon and cut (so that the knife stops when it hits the wood).
For larger potatoes - push a thin skewer right through the potato from end to end and towards the bottom. Cut through until the knife hits the skewer.