Bake an angel food cake. Cool completely. Remove from pan; place cake updisde downs. Slice off entire top of cake about 1 down; set aside.
Make cuts down into cake 1 inch from outer edge and 1 inch from edge of hold, leaving substantial “walls” on each side. With a curved knife or spoon, remove cake within cuts, being careful to a leave base of cake 1 inch thick. Place cake on serving plate.
In chilled bowl, beat 3 cups whipping cream, 1 teaspoon almond extract, 1 ½ cups confectioners sugar, ¾ cup cocoa and ¼ teaspoon salt until stiff. Fold ? cup toasted slivered blanched almonds into half the mixture; spoon into cake cavity.
Press mixture firmly into cavity to avoid holes in in cuts slices. Replace top of cake; press down gently.
Frost cake with remaining whipped cream mixture. Sprinkle with ? cup toasted slivered blanched almonds ove rthe side and top of cake. Chill at least 4 hours or until set.