Butter a shallow 3-quart baking dish; set aside. Position over rack in center and preheat oven to 450° F. Lightly oil potatoes and place on oven rack. Bake until soft, about 40 minutes for 8 ounce potatoes to 60 minutes for very large potatoes. Cool potatoes, then peel and mash well with 1/2 cup butter, sugar, marmalade and salt. Stir in 4 tablespoons liqueur.
Preheat oven to 350°. Spread mixture in prepared dish. Using a food processor fitted with steel blade, chop cookies coarsely. Aff remaining 1/4 cup butter and remaining 2 tbl. liqueur; pulse to make a coarse crumb mixture. Sprinkle potatoes. Bake assembled casserole until steaming hot, about 35 to 40 minutes.
Servings: 12
Final Comments
* Note: Canned sweet potatoes can be substituted for fresh.