Slice the potatoes
Clean and dry your sweet potatoes then slice them as thinly as possible. If you have a mandolin, use it. It's great if you get as equal slices as possible to assure the awesome chips crispiness.
Preheat the convection oven to 120 °C / 250 °F. Place a cast iron chip pan (or any other deep-sided cooking pan) over high heat. Pour in the vegetables oil and heat it until the oil reaches 175 °C / 350 °F. Add the thinly sliced sweet potatoes (use an aluminium basket for frying if you have it) and deep fry them for about 2 - 3 minutes. Remove the chips from the oil and place them on a paper towel-lined baking sheet.TipIt's important to regularly shake the pan the first minute to assure the crispiness.
Replace the kitchen towels with the new ones and place the baking sheet into the oven. Bake for 8 - 10 minutes.
Using a pestle and mortar smash the sprigs of rosemary and sea salt to get a nice, flavorful rosemary salt. Sprinkle the rosemary salt all over the sweet potato chips and enjoy.