Peppermint extract flavors the chocolate cake and the whipped cream frosting, while crushed peppermint candies sweeten the frosting and provide a festive holiday look.
Heat oven to 375°F. Lightly coat 15 x 10 x 1-inch baking pan with nonstick cooking spray; line bottom with waxed paper; coat with spray.
Sift together flour, cocoa powder, baking powder and salt into medium-size bowl.
Beat egg yolks in clean medium-size bowl until fluffy. Gradually add sugar, beating until thick and lemony, 3 to 5 minutes. Add 1 teaspoon peppermint extract; stir in the water. Fold in flour mixture.
Beat egg whites with clean beaters in clean medium-size bowl until stiff and glossy peaks form. Gently fold a spoonful of whites into yolk-flour mixture; fold in remaining whites. Spread evenly in prepared pan.
Bake in 375°F oven 12 minutes or until center springs back when lightly pressed with fingertip. Turn cake out onto wire rack. Gently peel away waxed paper; let cake cool completely. Then slice crosswise with serrated knife into 3 equal pieces.
Sprinkle gelatin over 1/4 cup cream in small saucepan; let stand to soften, 5 minutes. Place over low heat, stirring to dissolve gelatin, about 5 minutes. Let cool.
Beat gelatin-cream mixture with remaining 1-1/4 cups cream and 1 teaspoon peppermint extract in small bowl until stiff peaks form. Fold in crushed peppermint.
Place 1 cake section on platter; spread top with a third (about scant 1 cup) of peppermint cream. Stack with remaining cake and peppermint cream. Decorate with crushed peppermints, if desired.