Preheat oven to 350 F. Grease a 9x13 inches baking pan with cooking spray or butter and lightly dust with flour. In a large bowl, add flour, sugar, Ovaltine powder, instant coffee powder, baking powder, baking soda and salt. Whisk everything to combine.
Add milk, oil, egg and vanilla extract to the dry ingredients and mix everything to combine. Carefully pour the boiling water to the mixture and stir it with the rest of the batter. Pour the batter in the baking dish and bake for 20-25 minutes or until a toothpick inserted at the center of the cake comes out clean. Let cake cool completely.
Make the Vanilla Whipped Cream
In a bowl of a stand mixer, combine whipping cream and icing sugar. Beat at high speed until soft peaks form. Add the vanilla extract and continue beating until the cream is thick and fluffy. Spread the icing over the cooled cake.
Make the Ovaltine Icing
In the same bowl (no need to wash), combine the Ovaltine powder, cocoa powder and icing sugar. Gently pour the whipping cream and whisk the mixture at medium-high speed using the whisk attachment until a fluffy and thick icing forms. Spread icing over the vanilla whipped cream.