Step 1

Put the red onion, red pepper, garlic and ginger in a large bowl. Add the cornflour, then season with salt and pepper.

Step 2

Grate the sweet potato onto a clean teatowel or kitchen paper and squeeze out the excess liquid. Mix the grated potato into the ingredients in the bowl.

Step 3

Sift in the flour and mix well. Set aside for 5 minutes for the flour to absorb the moisture – you should be able to roll the mixture into a ball that sticks together. If there is too much moisture, mix in more flour, a tablespoon at a time, until it has a firmer hold.

Step 4

To make the dill mayonnaise, whisk the ingredients together with a tablespoon of water and a pinch of salt in a small bowl.

Step 5

Pour a teaspoon of rapeseed oil into a large frying pan and place over a high heat.

Step 6

Divide the sweet potato mixture into 8–10 balls, then flatten each one.

Step 7

Add 4–5 röstis to the pan and fry for 5–6 minutes on each side until crisp, browned and cooked through. Drain on kitchen paper and keep warm while you repeat with the remaining oil and röstis.

Step 8

Serve the röstis with the dill mayonnaise.