Put the flour with 2 teaspoons of salt in a bowl and add the cold butter in small pieces.
Rub everything crumbly with your fingers and add 2-3 tablespoons of cold water. Quickly shape the dough into a smooth ball and place well in an airtight bowl in the refrigerator for 30 minutes.
Preheat the oven to 180 ° C.
In the meantime, peel and finely chop the onions.
Heat the oil in a pan and fry the onions until translucent.
Also cut the mushrooms into small pieces and add to the onions together with the sprigs of thyme. Fry for about 5 minutes, season with salt and pepper and remove from heat.
Add 100g of the creme fraiche to the mushrooms and stir well.
Take the dough out of the refrigerator and divide it into four equal pieces. Roll out about 1mm thick and spread the mushrooms on top. Leave a 2-3cm wide border free, which is folded over onto the mushrooms.
Brush the folded edge with some vegetable drink and bake for 45 minutes.
Coarsely chop some parsley and serve on the galette with the remaining creme fraiche.