Preheat oven to 375°.
Melt 1 tablespoon butter in a large nonstick skillet over medium heat. Add leek; sauté 7 minutes or until tender and lightly browned. Set aside.
Place potato and garlic in a large saucepan; cover with water. Bring to a boil; cook 10 minutes or until potatoes are very tender. Drain. Place 1 tablespoon butter, potato mixture, 1/4 cup cheese, chives, and next 4 ingredients (chives through egg) in a large bowl; mash with a potato masher.
Lightly coat a 10 1/2-inch round removable-bottom tart pan with cooking spray. Unroll dough onto a lightly floured surface; let rest 5 minutes. Pat dough into bottom and up sides of pan. Spread the potato mixture into dough. Spread leek over potato mixture, and sprinkle with 1/4 cup cheese.
Bake at 375° for 20 minutes or until puffed and set. Cool in pan 5 minutes on a wire rack.