Heat a little clarified butter in a non-stick frying pan. Sauté the onions for approx. 5 mins., then the mushrooms for approx. 5 mins., season with salt. Set aside the mushrooms. Beat the eggs, milk and parsley, season. Heat a little clarified butter in the same pan. Pour the egg mixture into the pan, allow to solidify slightly. Using a spatula, push the eggs back and forth until just firm but still moist.
Lay out the tortillas. Spread the cheese, mushrooms, scrambled eggs and spinach in the middle. Fold the tortillas in from the side and roll up, tie with kitchen twine. Heat up the frying pan, cook the burritos for approx. 2 mins. on each side.