Spray 8-inch cast iron skillet or 9-inch pie pan with nonstick cooking spray. In medium saucepan, bring water to a boil. Stir in dip; mix well. Remove from heat. Add potato flakes and green chiles; mix well.
Spoon potato mixture evenly into sprayed skillet. Top with melted butter and 1/4 cup cheese.
Broil 4 to 6 inches from heat for 3 to 4 minutes or until cheese is bubbly and golden brown. Sprinkle with additional cheese. To serve, cut into wedges if desired.