This layered chocolate mousse cake is a lot easier to make then it looks. It is just a matter of making three things, the cake, the mousse and the glaze and layering them to create this fantastic dessert.
Preheat oven to 350F.
Grease and line a sheet pan with butter and parchment paper.
Whisk together flour, cocoa and salt. Set aside.
In a separate bowl whisk together milk, oil and vanilla. Set aside.
Whip eggs and sugar together until they are pale and creamy.
Alternating between flour mixture and milk mixture slowly fold in ingredients until well incorporated.
Pour batter into prepared sheet pan making sure to get an even layer of cake batter that reaches all the sides. Bake for 18 - 22 minutes or until an inserted toothpick comes out clean. Set to cool, once cool enough to touch turn whole cake over on a wire rack remove parchment and let cool completely.
In a glass measuring cup place rum, sprinkle gelatin over top and let sit for about 4 minutes, or until gelatin has softened. Heat up in a microwave doing 10 seconds at a time, stirring after each interval until gelatin has dissolved and has become smooth. Set aside.
Whisk together sugar and cocoa. Set aside.
Whip the cream till just before soft peaks form. Add sugar mixture and continuing whipping until it's incorporated. Take a third of whip cream and mix it into gelatin until its well combined, then place it back with the rest of whipped cream mixture and continuing whipping to stiff peaks.
In a small pot melt together water, chocolate chips and butter until smooth. Let cool.
Cut cake in half widthwise. Take half the mousse and spread a nice even layer. Place other piece of cake on top and spread another layer of mousse. Chill until mousse has set. Spread cooled glaze over top making a nice even layer. Chill for a couple of hours before serving. Serve.