Wash and finely chop the button mushrooms and onion.
Beat the eggs in a bowl, then season with salt and pepper.
Melt butter in a pan and sauté the onion and mushrooms.
When the mushrooms are cooked, add cream (fresh cream) and bring to a simmer.
Pour the beaten eggs into the pan and scramble them gently.
Top a slice of bread with the creamy mushrooms and scrambled eggs.
Cover with the remaining slice of bread and cut into pieces for easy eating.