Preheat your oven to 350°F (175°C). Grease two 8- or 9-inch cake pans with butter and line the bottoms with parchment paper.

In a large mixing bowl, whisk together all-purpose flour, Ghirardelli Sweet Ground Chocolate and Cocoa, granulated sugar, baking soda, cream of tartar, and salt.

In a separate bowl, combine buttermilk and softened butter, mixing on medium speed. Add eggs and vanilla extract, mixing until smooth.

Gradually add wet mixture to dry ingredients, mixing until just combined. Divide batter between prepared pans and bake for 30-45 minutes.

While cakes cool, make the buttercream frosting by creaming together softened butter and shortening. Gradually mix in confectioners' sugar and milk until smooth.

Once cakes are cool, slice out mini layers and stack them with a generous dollop of buttercream between each layer. Apply a thin coat of frosting over the entire outside of the cakes.

Decorate with pastel-colored frosting and colorful candies or sprinkles for a festive look.