Remove roots, outer leaves, and tops from leeks. Rinse under cold water; cut into 1 1/2 x 1/2-inch strips.
Combine leeks, lemon juice, olive oil, 1/4 teaspoon salt, and pepper in an 11 x 7-inch baking dish.
Bake at 500 for 20 minutes or until leeks are tender, stirring once. Spoon leek mixture into a bowl; set aside. Reduce oven temperature to 35
Coat baking dish with cooking spray, and arrange half of the potato slices in dish.
Spread leek mixture over potato slices. Top with remaining potato slices; sprinkle with 1/4 teaspoon salt.
Combine the milk and Spiced Pear Butter in a small bowl, stirring with a whisk until smooth; pour over potato slices. Cover loosely with foil; bake at 350 for 45 minutes. Uncover and bake 30 minutes.
Sprinkle with cheese, and bake an additional 10 minutes.