Preheat oven to 350° and line (3) 8 or 9 inch cake pans with parchement paper and spray with non stick spray. Set aside.
Pour boiling water into bowl with cocoa powder and whisk thoroughly until blended. Set aside.
Beat together flour, baking powder, baking soda, sugar, oil and eggs until smooth.
Beat in yogurt, followed by cocoa powder mixture until thoroughly mixed and no lumps remain.
Pour cake batter into three lined/sprayed 8 or 9 inch cake pans, and bake for 30-40 minutes. *Start checking at 30 minutes to make sure you don't overcook.
Once toothpick inserted and has come out clean, remove cakes from oven, let cool for a few minutes, then remove from pan and place on a wire rack to cool.
In a large bowl, beat all ingredients together until smooth and fluffy. Start with 3 cups of powdered sugar and gradually add more until the right consistence is obtained. If you add too much, balance it out with more milk, 1 Tbsp at a time.
Cut the tops off each layer so that they are flat. Place the first layer on a serving dish, then "plop" a generous scoop of icing on top. Spread out from the middle until you have a solid layer.
Gently put the second layer on top, and repeat the icing process.
Repeat with a final layer, and spread icing on top to form a smooth layer.
To ice your sides, spread small spoonfuls all over the sides of the cake, and with a long icing spreader or paddle, scrape the sides all the way around so that you have a "bare" iced look. This step doesn't have to be perfect, so make it look however you like.
Top with sprinkles or decorations of your choice. Cut and serve.
Notes: Cake can be made into three thick layers or four smaller layers - great to customize.
Want flavoring? Add some strawberry flavoring oil or other flavors to the icing when mixing.
Customize this cake by adding as much or as little decorations as you like, including edge icing, different sprinkles, mini chocolate chips, or fresh fruit such as berries on top.