Grease bottom and sides of a 15" x 10" jellyroll pan; line with wax paper; grease and flour wax paper. Set aside.
Combine flour, baking powder, and salt, stirring well. Set aside.
Beat egg whites at high speed with an electric mixer until foamy. Gradually add 1/4 cup sugar, 1 tablespoon at a time, beating until stiff peaks form and sugar dissolves (2 to 4 minutes). Set aside.
Beat egg yolks in a large mixing bowl at high speed, gradually adding 1/2 cup sugar; beat 5 minutes or until thick and pale. Add water, orange rind, and flavorings; beat well. Add flour mixture, and beat just until blended. Fold in about one-third of egg white mixture. Gently fold in remaining egg white mixture. Spread batter evenly into prepared pan.
Bake at 375° for 10 minutes or until top springs back when lightly touched.
Sift 3 tablespoons powdered sugar in a 15" x 10" rectangle on a cloth towel; set aside. When cake is done, immediately loosen from sides of pan, and turn out onto sugared towel. Peel off wax paper. Starting at narrow end, roll up cake and towel together; cool completely on a wire rack, seam side down.
While cake cools, stir coffee granules into milk until coffee granules dissolve. Combine 3 3/4 cups powdered sugar and cocoa in a large bowl, stirring well with a wire whisk. Add coffee mixture and butter to sugar mixture; beat at medium speed until smooth.
Unroll cake and remove towel. Spread cake with half of frosting; carefully reroll. Cut a 1" thick diagonal slice from 1 end of cake roll. Place cake roll on a serving plate, seam side down; position cut piece against side of cake roll to resemble a knot, using a little frosting to "glue" it in place. Spread remaining frosting over cake and knot. Score frosting with the tines of a fork to resemble tree bark. Chill cake before serving if frosting is soft. Garnish, if desired.