Hasselback-style potatoes cook more quickly than whole potatoes, and the slices allow for more flavours, like spices, herbs or grated Parmesan during the final minutes of cooking.
Preheat the oven to 425˚F.
Slice the potatoes crosswise at 1/4-inch intervals, without slicing through to the bottom—placing a wooden spoon on either side of the potato will stabilize it and prevent your knife from cutting all the way through.
Place them cut side up in a baking dish, brush all over with the oil, drizzle with butter, sprinkle with salt and bake for 30 minutes.
Remove from the oven and sprinkle with your favourite spice blend, fresh herbs or freshly grated Parmesan cheese and return to the oven for 5-10 minutes, until the potatoes are tender.