With a little olive oil, fry the mushroom with half a clove of garlic & 4 sprigs of thyme, tear off the leaves & discard the stalks. Keep on a low heat for best results, turning frequently. Season well. Once cooked, put aside.
Using the same pan, cook the onion in the same fashion as the mushrooms, with thyme, garlic & seasoning. Whilst this is frying, put your potato matchsticks on a large plate, spaced out evenly & pop in the microwave for 2 minutes, then give them a little shake and pop back in for another 2 mins 30 seconds.
In a small circular, non stick frying pan, add a little oil. Place half of your potatoes in the bottom and wet your spatula before pressing the potato down (this is because the potato gets quite sticky caused by its starch). Pour the onions on top of the lower layer of potato & then place the rest of the ‘matchsticks’ on top. Again, wetting spatula & pressing down firmly.
Cook on a low heat so that the potato crisps gradually whilst also cooking the middle of the Rosti. Around 8-10 minutes on each side. Flip Rosti over by carefully using either a plate or chopping board on top of pan & slowly turning upside down & then slide the Rosti, cooked side up, back into the pan.
Once cooked, serve with a dollop of Creme fraiche, the scattered mushroom slices & a few remaining sprigs of thyme. Enjoy the match!