Peppermint Cream-filled Cake

Some asked for the recipe for Kali's birthday cake, so here it is:

Peppermint Cream-filled Cake
From Betty Crocker's Chocolate Cookbook

For the cake:
1/2 C. cocoa
3/4 C. boiling water
1-3/4 C. sugar
1-1/2 C. flour
1-1/2 t. baking soda
1 t. salt
1/2 C. vegetable oil
2 t. vanilla
7 egg yolks
1 C. egg whites (about 7-8)
1/2 t. cream of tartar

For the Peppermint Cream:
1 C. powdered sugar/icing sugar
2 C. chilled whipping cream
1 t. peppermint extract
6-8 drops food colouring

Heat oven to 325F.
Mix cocoa and boiling water; let stand until cool.
Mix sugar, flour, baking soda, and salt in 3-qt. bowl. Beat in cocoa mixture, oil, vanilla, and egg yolks with spoon until smooth.
Beat egg whites and cream of tartar in a 3-qt. bowl on medium speed until stiff peaks form. Pour egg yolk mixture gradually over beaten egg whites, folding with rubber spatula just until blended.
Pour into UNGREASED tube pan, 10x4 inches.

Bake until top springs back when touched lightly, about 1 hr., 15 min.
Invert pan on heat-proof funnel (or on a glass bottle with a thin neck); let hang until cake is cold.

Remove cake from pan; place cake upside down.
Slice off top of cake about 1 inch down; reserve top.
Make cuts down into cake 1 inch from outer edge and 1 inch from edge of hole, leaving substantial "walls" on each side.
Remove cake within cuts with a small spoon, being careful to leave a base of cake 1 inch thick.

Prepare Peppermint Cream, beating all the ingredients together in a chilled bowl until stiff.
Spoon mixture into the cake cavity.
Replace top of cake; press gently.
Frost side and top of cake with remaining Peppermint Cream.
Just before serving, garnish with chocolate leaf mints, crushed peppermint candy, chocolate shavings, or other garnish of your choice.

Keep uneaten cake refrigerated.

Enjoy!