Preheat oven to 350°F. In medium sauce pan, melt butter. Add milk and 2 tablespoon taco seasoning. Remove from heat and add potato flakes until incorporated. Press mixture into bottom of a 10 inch pan. Bake for 7-10 minutes until it just barely turns golden brown. In medium skillet cook beef and onions until beef is browned and cooked through. Drain. Add salsa and remaining taco seasoning. Cook until bubbly. Poi into crust. Bake for 15 minutes or until crust is golden brown. Let cool for 5 minutes. Top with cheese, lettuce, tomatoes and olives. Cut and serve with sour cream.