1Heat oven to 350°F. Line 9-inch square pan with foil, leaving 1 inch of foil overhanging at 2 opposite sides of pan; lightly spray foil with cooking spray. In large bowl, stir cookie mix, butter and egg with spoon until blended. Press dough into pan.
2Bake 20 to 22 minutes or until set and edges are lightly browned. Sprinkle with marshmallows. Set oven control to broil. Broil 4 to 6 inches from heat 1 minute or until marshmallows are toasted. Cool 20 minutes.
3Meanwhile, in 1-quart saucepan, heat brown sugar, 3 tablespoons butter, the corn syrup and salt to boiling; boil 1 minute. Stir in whipping cream; cook 1 minute. Remove from heat; cool 10 minutes, stirring occasionally. Drizzle caramel sauce over bars; sprinkle with pecans. Cool completely in pan on cooling rack, about 1 hour 30 minutes. Use foil to lift from pan. Cut into 4 rows by 4 rows.