go shopping for these ingredients :

2 1/2 cups sugar
16 ounces marzipan
20 ounces (5 sticks) unsalted butter, slightly softened
2 teaspoons vanilla extract
12 eggs
2 1/2 cups flour
3 teaspoons baking powder
1 teaspoon salt
1 teaspoon ground ginger
Confectioners' sugar for rolling fondant
Butter cream, recipe follows
2 pounds fondant
Red, blue and yellow food coloring
Royal icing, recipe follows
Butter Cream:
7 cups sugar
2 cups water
24 egg yolks
4 pounds (16 sticks) unsalted butter, softened

Cooking Recipe:

Heat oven to 350 degrees F. Butter and flour an 8 by 2-inch round pan and a 9 by 9 by 2-inch square pan. mix or combine the sugar and marzipan in a food processor. Pulse until combined into fine crumbs. Cream the buutter in a mixer fitted with a paddle attachment (or using a hand mixer) until smooth. Add the sugar-marzipan mixture and mix. Add the vanilla and mix. Add the eggs two at a time, mixing after each one. Sift the flour, baking powder, salt, and ginger together. Working in batches, add the dry ingredients to the marzipan mixture, mixing after each addition just until combined. Bake for 20 to 30 minutes, until a tester inserted into the center comes out dry and clean (a few crumbs are okay) and let cool in the pan.
Butter Cream: Combine sugar and water and bring to a boil on a medium saucepan. Boil until a candy thermometer registers 240 degrees F. Whip egg yolks until light and fluffy and carefully pour the sugar water mixture into the yolks while the mixer is running at a moderate speed. Continue whipping until cooled. Add softened butter in small batches, stopping after each addition. Remove the 8-inch cake from the pan, and cut a 5-inch and a 3-inch circle of cake from the 9-inch pan. Cover them with butter cream and freeze. Dye fondant pastel pink, blue and yellow by kneading food coloring into it. Roll out on a powdered sugared surface and cut 1 circle out of each color to cover 1 layer of the cake, leaving 2 extra inches to hang over sides. Lay the fondant over the cake layers and with your hands, mold the fondant over the cake to fit. Trim the edge and tuck it slightly under the cake. On a large cake platter, stack the layers and run a long skewer down the center.

Royal Icing:
2 cups powdered sugar
3 to 4 tablespoons egg whites*

Royal Icing: Whip together powdered sugar and 3 to 4 tablespoons of the egg whites so it's pipe-able but not too thin that (or this, whichever) it runs on the cake. Decorate cake with piped royal icing using a plain small tip, starting at the bottom layer. You can embellish with silver balls, gum paste flowers on top, etc.

*RAW EGG WARNING
Food Network Kitchens suggest caution in consuming raw and lightly-cooked eggs due to the slight risk of Salmonella or other food-borne illness. To reduce this risk, we recommend you use only fresh, properly-refrigerated, clean, grade A or AA eggs with intact shells, and avoid contact between the yolks or whites and the shell.