Unscrew the mushroom stems and chop finely. Brush the mushroom heads with the olive oil, salt and pepper. Fry the bacon and mushroom stalks in oil until golden brown. Add spring onions, cook for 1-2 minutes and let cool.
Beat the eggs with the crème fraiche and cheese until smooth. Add the bacon and onion mixture and season with salt and pepper. Pour the mixture into the mushroom heads and fry in the hot oven at 210 degrees on the 2nd rack from the bottom for about 15 minutes.
Tip: Prepare on the grill and serve as a starter or intermediate course at the BBQ.