Cover potatoes with water; boil and simmer 15 to 18 minutes until very tender. Drain thoroughly; steam-dry 3 minutes.
Mash smooth with cream cheese, filling butter, half-and-half, sugar, salt, ginger, and vanilla. Grease a shallow 2-quart metal pan; spread evenly.
Cool briefly; refrigerate within 2 hours. Once cold, tightly cover with foil, seal in a freezer bag, and freeze up to 1 month. Store dry cookie crumbs separately airtight.
Fully thaw refrigerated 24 to 36 hours. Heat oven to 350°F; bake covered 50 to 60 minutes until hot at center.
Mix crumbs and topping butter; scatter on uncovered casserole. Bake 10 to 15 minutes more until crisp and center reaches 165°F. Rest 10 minutes.