1 (16 ounce) package 1-step angel food cake mix
3 tablespoons unsweetened cocoa powder, divided
1 tablespoon instant coffee granules
1/4 cup powdered sugar
3 tablespoons hot water
1 pint coffee ice cream (regular or low-fat)
1 1/2 cups frozen fat-free whipped topping
1/4 cup chocolate syrup
Preheat oven to 325 degrees F. Using parchment paper or waxed paper, line bottom and sides of a 10 x 15-inch cookie sheet (one with raised sides).
Prepare three-fourths of the cake mix - following package directions but using only 2 cups of the mix and 1 cup of water. Pour the batter into the prepared pan, spreading evenly. (Or make the entire batch of batter, and pour three quarters of it - about 5 1/2 cups - into the prepared pan and the remainder into a small loaf pan to bake and eat separately.)
Bake about 20 minutes or until top springs back when lightly touched with fingertip and toothpick inserted near the center comes out clean. Remove the cake from the oven, set it on a rack and sprinkle it with 2 tablespoons of the cocoa powder. Cover with a clean flour-sack-type kitchen towel (or a sheet of parchment paper slightly larger than the size of the pan) and in one quick motion, holding the towel or parchment in place at both ends, invert all onto the counter. Lift away the pan and immediately but carefully peel away the paper, starting at one end.
Fold one end of the towel (or the new parchment paper) up over that end of the cake and roll up the cake and the towel or paper together. Yes, the towel or paper gets rolled inside cake. Set aside to cool completely, about an hour.
Meanwhile, combine coffee granules, remaining tablespoon cocoa powder, powdered sugar and hot water, stirring until all is completely dissolved; chill.
When cake has cooled, gently unroll it onto a cookie sheet and set in the refrigerator 30 minutes to chill (to minimize ice cream melt during assembly). Meanwhile, soften the ice cream in the refrigerator 20 or 30 minutes and the whipped topping for the last 15 minutes of that, scooping each into small chunks in separate bowls and stirring occasionally. Proceed when ice cream is still very cold and just barely spreadable. Have topping and syrup ready. (Also have space cleared in freezer.)
Position a large sheet of plastic wrap or foil at the far end of the cake, tucked under the end. Stir coffee-sugar mixture and brush onto chilled cake. Working quickly, scoop ice cream onto cake and spread evenly. Spread topping over ice cream. Pour chocolate syrup over topping and spread. Gently re-roll cake without the towel or parchment, rolling the finished roll onto the plastic or foil. Wrap plastic or foil around roll, set on pan or flat plate and freeze for at least 4 hours. Unwrap and let stand 5 minutes at room temperature before slicing to serve.