Preheat your oven to 350°F (175°C). Grease and flour two 6-inch round cake pans.

In a mixing bowl, whisk together flour, Ghirardelli cocoa, granulated sugar, baking soda, cream of tartar, and salt.

Add the buttermilk and softened butter; beat with an electric mixer for 2 minutes. Incorporate more buttermilk, eggs, and vanilla.

Pour the batter into the prepared pans and bake for 30-45 minutes. Let cool for 10-15 minutes before transferring to wire racks.

To make the frosting, cream together softened butter and shortening. Gradually add confectioners' sugar and milk to achieve desired consistency.

Once cooled, slice each cake into two layers and layer with frosting in between. Apply a crumb coat of frosting.

Frost the outer layer and decorate with festive toppings such as sprinkles or mini chocolate eggs.