Cover chicken in a large pot with water and boil until done (45 minutes or so). Season to taste with garlic salt and pepper and any other spices you like.
Add bacon to a large skillet over medium-high heat and cook until it starts to brown. Dice yellow onion and add to skillet and cook until it begins to turn translucent. Once chicken is cooked through, remove from water (do not drain the water) and put in a bowl to cool. To boiling water, add spaghetti and cook to al dente. Shred cooled chicken and add to skillet. Last add mushrooms and combine all until cooked through.
Drain all but a cup of cooking liquid from spaghetti. To cooked spaghetti add diced velveeta and cream cheese. Cook over low and stir frequently until all the cheese is melted. Add contents of skillet to the cheesy spaghetti and mix well. Serve with garlic bread and salad!