In a large glass bowl, beat the heavy whipping cream until it begins to thicken. Carefully add the powdered sugar and cocoa gradually and continue whipping. I find the best way to do this is to place the bowl in the kitchen sink and whip with a hand mixer so that when it splatters, it doesn’t get the entire kitchen messy. The cocoa will look like it is separating and lumpy but continue to beat until stiff peaks form and by then, the cocoa should be evenly combined. (If you are worried about lumps you can sift in the cocoa and powdered sugar with a fine mesh sieve.) The frosting should be thick and spreadable – but not overly whipped or it will look a bit curdly. Just beat to stiff peaks.
When the angel food cake has been baked and cooled completely, follow the pictures below and cut the cake in half to form two round circles. Lay the top half to the side and gently remove pieces of the angel food cake to form a ditch in the bottom portion of the cake (taking care not to dig all the way to the bottom of the cake, you want a layer of cake on the bottom underneath the ditch). Spoon frosting into the ditch you made and lay the top circle of cake back on top. Frost the sides, top and middle of the cake. Top with toasted almonds.
Refrigerate until time to serve. A serrated knife works best to cut the cake into slice