Rinse the chicken breast fillets, pat dry, and cut into strips
Pluck the parsley leaves and chop them
Heat 3 tablespoons of oil in a large pan over medium-high heat and fry the mushroom slices until golden brown, about 5-7 min
Transfer the mushrooms to a plate and wipe the pan clean
Heat 2 tablespoons of oil in the pan over medium-high heat and fry the chicken strips until light brown and cooked through (internal temperature 74°C / 165°F), about 8-10 min, seasoning with salt and pepper
Add the diced onion and fry for about 2 min
Deglaze the pan with the white wine and let it reduce for about 3-5 min
Add the chicken broth and cream to the pan and bring to a boil
Season the sauce with salt and pepper to taste
Meanwhile, cook the spaetzle in plenty of boiling salted water according to the packet instructions
Mix the cooked mushrooms back into the sauce
Drain the spaetzle
Serve the spaetzle topped with the chicken and sauce, sprinkled with chopped parsley