Heat oven to 350°F. Grease and flour 12-cup fluted tube cake pan. In large bowl, combine sugar, brown sugar and 3/4 cup butter; beat until smooth. Add 3/4 cup syrup and eggs; blend well.
Lightly spoon flour into measuring cup; level off. Add flour, baking powder, cinnamon, salt, nutmeg and allspice; mix well. Stir in apples and 1/2 cup walnuts. Spoon into greased and floured pan.
Bake at 350°F. for 55 to 65 minutes or until toothpick inserted in center comes out clean. Cool 15 minutes. Remove from pan. Cool 1 hour or until completely cooled.
In small bowl, combine powdered sugar, 3 tablespoons syrup and 1 tablespoon butter; mix until smooth. Spoon over top of cake. Sprinkle with 1 tablespoon walnuts.