6 ounces cream cheese, cut into small pieces, room temperature
2¼ cups sugar
â…” cup water
½ cup (1 stick) plus 1 tablespoon unsalted butter, cut into ½-inch cubes
1½ cups walnuts, toasted, chopped
1 teaspoon grated orange peel
Thin orange peel strips
Vanilla ice cream
Position rack in center of oven and preheat to 350°. Butter and flour two 9-inch diameter cake pans with 1 ½ inch-high sides.
Sift first 8 ingredients into medium bowl. Using electric mixer, beat sugar and oil in large bowl until well blended, about 2 minutes. Add eggs 1 at a time, beating well after each addition. Add pumpkin and vanilla; beat until blended. Gradually add dry ingredients; beat just until incorporated. Divide batter between prepared pans; smooth top with spatula.
Bake cakes until tester inserted into center comes out clean, about 30 minutes. Cool completely in pans on racks. Run small knife around cakes to loosen. Turn cakes out onto racks.
Icing and Filling
Stir rum, raisins, and dried cranberries in small saucepan over low heat just until warm, about 1 minute. Remove from heat; let stand 30 minutes. Drain, reserving rum and fruit separately.
Whisk whipping cream and cream cheese in small bowl until smooth. Combine sugar and 2/3 cup water in heavy medium saucepan. Stir over medium-low heat until sugar dissolves. Increase heat to high; boil without stirring until syrup is deep amber color, occasionally brushing down sides of pan with pastry brush dipped in water and swirling pan, about 10 minutes.
Slowly and carefully whisk in cream cheese mixture (caramel mixture will bubble vigorously). Add butter; whisk until mixture is smooth, about 1 minute. Remove from heat; cool caramel icing 10 minutes, whisking occasionally.
Pour ¾ cup warm caramel icing mixture into bowl. Mix in half of reserved dried fruit mixture, 1 cup walnuts and grated orange peel.
Place 1 cake layer on 8-inch diameter tart pan bottom or cardboard round. Brush top of cake with half or reserved rum. Spread caramel-nut filling over, leaving ½ inch plain border at edges. Top with second cake layer, flat side down; press to adhere. Brush top of cake with remaining rum; let stand 10 minutes to allow rum to soak in.
Pour generous ½ cup warm caramel icing onto cake and, if necessary, spread over top with offset spatula to cover. Refrigerate cake and remaining caramel icing until icing is firm enough to spread and to adhere to sides of cake, stirring occasionally, about 1 hour.
Transfer ¾ cup chilled icing to small bowl and chill for sauce. Using offset spatula, spread remaining 1 cup icing evenly over sides of cake to cover.
Mix remaining dried fruit mixture and remaining ½ cup walnuts in another small bowl. Sprinkle mixture in 1 ½ inch-wide border around top edge of cake. Cover cake with cake dome and chill at least 6 hours. (Can be made 2 days ahead. Keep cake and caramel icing for sauce chilled separately.)
Place cake on platter. Garnish with orange peel. Rewarm icing over low heat just until pourable. Serve cake cold with ice cream and warm caramel sauce.