Spiralize the potato and cook in 1 tsp of the oil for 5 minutes to soften then pour into a bowl.
Add one beaten egg to the potato and pour into a ramekin dish. Cover with greaseproof paper and place a can on top to weigh the mix down. Pop in the fridge for 15 mins.
When ready to cook heat the remaining 1/2 tsp oil and add the squashed down rosti mix to the pan to brown gently and cook through.
Put a small pan of water on to boil and turn down to a simmer. When you turn the rosti over to cook the other side put the egg in to poach and add the chorizo slices and cherry tomatoes to the rosti pan.