Salt and pepper each prime rib section thoroughly. Heat butter and oil in a large saute pan over medium-high heat. Brown the seasoned meat until the skin is browned and lightly crisp. Reduce heat to low and allow the meat to saute for approximately 20 minutes, turning every few minutes, until cooked to desired temperature.
Pour 2 cups of beef stock and 1 cup of red wine into a medium sized saucepan. Simmer the liquids over medium heat for approximately 20 to 30 minutes, or until the mixture is slightly reduced. Add sliced mushrooms and salt and pepper, to the sauce, and reduce the mixture for an additional 5 minutes.
Heat a grill pan over medium heat. Coat the bottom of the pan with olive oil. Add the sliced squash and carrots to the pan and grill until they become slightly tender. Remove the vegetables from the heat and seasson with salt and pepper immediately.
In a large pot, bring enough water to cover 2 potatoes to a rolling boil. Boil the potatoes in the water until they are soft. Drain the water from the pot and mash the potatoes. Add milk, butter and garlic salt to the pot. Mash all of the ingredients together until you reach the desired creaminess.