Preheat a nonstick pan over medium heat with some olive oil.
Preheat a grill pan over medium/high heat with some olive oil.
Meanwhile combine the creme fraiche/yogurt, lemon juice, lemon zest and fresh mint in a small bowl. Set aside.
Grate the sweet potato and combine with salt.
Form small patties out of the sweet potato and add to the nonstick pan, fry for 2-4 minutes on each side until golden brown. Don't flip too early, then they might break.
Pat dry the prawns using a paper towl.
When you have flipped the hash browns add the prawns and garlic (if using) to the grill pan and fry for 1-2 minutes on each side.
When sweet potato hash browns are ready put on a plate, top with the mint dressing, add a prawns on top of each hash brown and the add crumbled feta cheese on top.