Heat your oven to 450 degrees with the rack in the center.
In a small bowl combine the blue cheese dressing, the minced garlic, white pepper, Italian spice mix , salt, olive oil & dry rosemary. Mix well.
Place the chicken legs in a large skillet & pour in the marinade. Marinate the chicken legs for 10 – 20 minutes or for up to 5 hours for really strong flavor.
Put the skillet with the chicken legs in the oven and bake 10 minutes. When the legs begin to brown, remove from the oven & add the sliced mushrooms. Pour in the chicken broth.
Put again in the oven and bake another 10-15 minutes.