Angel Food Cake with Mocha Icing

Another recipe from my grandma that brings back memories of being little and hanging out at her house.  I adore angel food cake, and even more with her mocha icing smothering it!  I mean, seriously, how can't you love that combo?!

CAKE:                                                                           MOCHA BUTTERCREAM:
1 1/2 c powdered sugar (10x)                                           1 1/2 c butter
1 c cake flour                                                                    4 Tbs instant coffee
10 lg egg whites                                                                 2 Tbs sifted cocoa
1 1/2 tsp cream of tartar                                                    2 c powdered sugar
3/4 c sugar                                                                         chocolate sprinkles

Sift all dry ingred. for cake.
In large bowl, whisk egg whites till soft peaks form.  Add cream of tartar.  Gradually add in sugar whisking all the time.  Sift 1/3 of flour mix over whites, lightly folding in.  Repeat till all flour is mixed in.
Turn batter into a large ungreased tube pan.  Smooth top.
Bake at 350 for 40 min. or until done.
Cool cake by inverting on a bottle neck so it hangs upside down.
Once completely cooled, loosen edges & remove from pan.

To make icing, beat butter till very soft & smooth.  Add rest of ingred. & beat until well combined & light.
If you want to slice the cake into two layers, use a large bread knife that is serrated. 
Spread icing between layers & all over the tops & sides.
Garnish with sprinkles!