Preheat the oven to 400 F/ 200 C/ fan 190 C/ gas mark 6.
Scrub the sweet potatoes to remove some of the skin and soften it. Place each potato in between the handles of 2 wooden spoons/spatulas and cut into thin slices (approx. ¼ inch thick) ⅔ of the way through. Take care when slicing the ends of the potatoes as the knife may cut all the way through.
Combine the rest of the ingredients and drizzle the mixture (use only half for now) over the potatoes making sure it gets in between the slices (use a basting brush to do this).
Place on a baking sheet or in a roasting pan and bake in the centre of the oven for approx. 40-45 minutes or until tender. Halfway through baking remove from the oven and drizzle over the rest of the oil mixture. Cover loosely with parchment paper if the potatoes start to brown too much.
Remove from the oven and serve immediately.
Notes
I recommend using medium size, round rather than thin sweet potatoes. It will be easier to coat them with the herb dressing without separating the slices.
Use a vegetable scrubber or brush to remove some of the tough skin from the sweet potato before cutting it.
Use your favourite herb combination, not necessarily my suggestions.
Take care when slicing the ends of the potatoes as the knife may slice all the way through.
If your sweet potatoes start to brown too much in the oven cover them loosely with parchment paper and continue baking until tender.
Best served immediately.
Freeze your hasselback sweet potatoes, once completely cooled, in an airtight container for up to 3 months.