Preheat the oven to 350 degrees and spray two 8 inch (or three 6 inch) cake pans with non-stick spray and line with parchment paper.

In a large bowl, combine flour, cocoa powder, baking soda, baking powder, and salt. Whisk to combine, then set aside.

In another large bowl, combine sugar, eggs, yogurt, oil, and vanilla. Using an electric hand-held mixer, mix on medium low speed until fully incorporated. Add half of the flour mixture and half of the buttermilk. Mix on low speed until just combined. Then add the rest of the flour and buttermilk and mix until fully combined.

Divide batter between the prepared pans and bake for 20-22 minutes, or until the centers are set and a toothpick inserted into the center of each cake comes out clean. Let the cakes cool in the pans for 10 minutes, then turn out onto a wire rack to cool completely.

In the bowl of a stand mixer, or large bowl with an electric mixer, beat butter on medium speed until smooth and creamy. Add vanilla extract, milk, and half of the powdered sugar. Mix on low speed until fully incorporated. Repeat with the second half of the powdered sugar and continue to beat for one minute.

(Repeat this process for the chocolate and dark chocolate frostings.)

Place a cake layer on a cake plate or stand and spread a thin layer of frosting on top. Repeat with the other two cake layers and cover the entire cake in a thin crumb coat. Place the cake in the freezer while you prepare the rest of the decorations.

Put each frosting in a pastry bag with a grass/fur tip. I used a small star tip to go around the outside of the cake, and two grass tips for the fur on top of the cake. Using the modeling dough to make two ears, two eyes, and a nose. I sort of free handed these and made them proportional to the size of the cake. You may need to use leftover modeling dough to create to flat/ball pieces to place under the ears to make them stick up a bit.

Remove the cake from the freezer. Cover the sides with dark chocolate frosting. (Orange border around the bottom is optional.) Then cover the tops of the ears and head with chocolate frosting. Next I piped the white frosting, which is used for the muzzle area, the "eyebrows", and the fur on the edges of the cheeks. After that, fill in the rest of the space with chocolate frosting. Place the nose and eyes on the cake. And ta da!