Preheat the oven to 350 degrees. Spray two 8 inch cake pans with baking spray and dust with cocoa powder.

To make the syrup combine the sugar, heavy whipping cream, salt, vanilla, and cocoa powder in a small saucepan. Bring to a boil over medium high heat.

Remove from the heat and set aside to cool.

In a large bowl combine the flour, sugar, baking soda, baking powder, salt, and cocoa powder.

Add in the melted chocolate, yogurt, butter, and eggs. Mix well until moistened and no lumps remain. Be careful not to overmix.

Divide the batter between the two pans. Bake for 35-40 minutes or until a toothpick inserted into the center comes out clean.

Using a skewer, poke holes in the cake in 1 inch intervals. Gently pour the syrup over top of the cakes and use a spoon to spread it over the top and into the holes.

Set the cakes aside and allow to cool completely.

To make the frosting combine the butter, Nutella, and 2 cups of powdered sugar in a large bowl. Beat with an electric mixer on low speed until creamy. Continue adding in the remaining sugar, a half cup at a time, until frosting is desired consistency. Stir in the vanilla.

Run a knife around the cake layers to loosen them. Remove the cakes form the pans.

Place the first layer on a cake round. Spread 3/4 cup of frosting on top of the first layer and top with the second layer. Use remaining frosting to frost the top and sides of the cake.