Preheat the oven to 200'C.
Roll the pastry out on to a lined baking sheet and prick with a fork. Cover with a second sheet of baking parchment and a second baking sheet (this will keep the pastry flat as it cooks), transfer to the oven and bake for 20 minutes.
Once the pastry is cooked, remove from the oven and cut into 6 discs whilst still warm. Place on a wire rack and allow to cool.
Wash the spinach and pat dry. Clean and slice the mushrooms. Peel and finely dice the garlic.
Melt the butter in saucepan and allow to foam. Add the garlic and cook for a minute or so before adding the spinach leaves. Cook for a minute and then season with salt and pepper. Place in a colander to allow the liquid to drain.
Add a little more butter to the same pan and then cook the mushrooms over a low heat for 2 minutes. Season with salt and pepper.
Cut each Saint-Marcellin cheese half to give two rounds. Place a tablespoon of creme fraiche on top of each puff pastry disc and top with spinach and mushrooms. Place a round of cheese on top and then place in the oven to melt a little. Serve immediately.
«This recipe also works well with sliced tomato in summer.»