"The ultimate princess doll cake is not as hard to make as it looks! Make it out of your favorite sponge cake and frosting recipes, or use store-bought cakes and icing and focus on the decorating! Your little princess will love this doll cake."
Preheat oven to 350 degrees F (175 degrees C). Grease four 8-inch springform pans and line with parchment paper.
Combine 1 cup plus 6 tablespoons butter and sugar in a large bowl; beat with an electric mixer until smooth and creamy. Add eggs, one at a time, beating well after each addition. Sift flour in gradually and add the vanilla extract, beating until smooth. Distribute batter evenly between the 4 prepared pans.
Bake in the preheated oven until a skewer inserted in the center comes out clean, 25 to 35 minutes. Cool in the pans for 10 minutes. Remove rings and transfer cakes to wire racks. Cool completely before decorating, about 1 hour.
Cut out a 2-inch hole from the center of each cooled cake using a round cutter of glass, large enough for the doll to fit through.
Glue cake board onto a revolving cake stand using a small amount of frosting. Spread 2 tablespoons of frosting on the cake board and lay the first cake on top. Repeat with remaining cake layers, aligning the holes in the center; cake should reach the hips of the doll. Insert 4 straws 1/2 inch from the hole, piercing all the way through the layers, to add stability. Cut off the ends of the straws sticking out from the cake with scissors.
Measure 1/2 inch from the top edge of the cake using a ruler, rotating the cake and making marks with a skewer. Trim off the edge at an angle to create a dome-shaped skirt.
Color 2/3 of the vanilla frosting in a bowl with a few drops of pink food coloring. Frost entire cake with a thin layer of frosting, including inside the hole in the center using a thin spatula. Refrigerate cake for 30 minutes to 1 hour to set the first coat.
Fill a piping bag with a large flat tip with frosting. Pipe frosting around the cake, working from the bottom up, until it is fully covered. Immerse a long icing spatula in hot water and dry thoroughly with a kitchen towel. Smooth frosting with the warm spatula for a polished, smooth finish. Repeat process until frosting is smooth. Chill cake in the fridge for at least 1 hour and up to overnight.
Wrap the doll's legs with plastic wrap and insert doll into the hole, adding frosting to the hole if necessary to keep the doll in place.
Divide remaining frosting into different bowls and color pink, green, and/or leave some white. Use the skewer to trace where you intend to pipe any patterns, bows, or other design elements over the frosting.
Fit a small star tip on a piping bag and fill it with white or light pink frosting. Holding the bag almost perpendicular to the cake, make rows of small stars for the front of the dress. Work from the bottom up. Pipe more stars directly onto the doll from the waist up to make the top of the dress.
Use a ruffle tip to create ruffles, ribbons, and bows. Use a small star tip to create rosettes all over the skirt of the dress. Use a leaf tip with green icing to add leaves. Keep completed cake in the refrigerator until serving.