Preheat oven to 350oF (175 °C). Line up the baking sheet 12x17 inch with parchment paper or a baking mat.
In the large mixing bowl, sift together flour, baking powder, and cocoa powder. Set aside.
In a separate mixing bowl, whisk eggs with sugar until light and fluffy.
Add vegetable oil and mix until all combined.
Add dry ingredients and fold with the spatula. Do not overmix.
Transfer the batter to a baking sheet and level up with the spatula.
Bake at 350oF (175oC) for 10-15 minutes or until the toothpick inserted into the center comes out clean. Let cool for a few minutes, then transfer to a wire rack to cool completely.
Using a heart cookie cutter, cut the chocolate sponge.
How to Make Strawberry Confit
In a small cup or mixing bowl, mix sugar and pectin NH.
In the small saucepan, add strawberries puree and warm up over medium heat to 40oC (104oF).
Drizzle the sugar mixture over the puree and wait until it boils, mixing with the whisk all the time. When the mixture starts boiling, wait 20-30 seconds and turn off the heat.
Add a pinch of citric acid and mix with the whisk.
Transfer the confit into silicon forms and keep in the freezer until assembly.
How to Make Chocolate Mousse
In the small mixing bowl or cup, mix powdered gelatin and cold water. Mix well and set aside.
Place chocolate in the tall cup.
In the small saucepan, over medium heat, bring to boil heavy cream 1, but do not boil.
Add warm mixture over the chocolate and let it sit for a few minutes.
Add gelatin mass to the chocolate mixture and emulsify with an immersion blender. Let the mixture cool to 90oF (32oC).
In the mixing bowl, lightly whip cold heavy cream 2.
Using a spatula, gently fold in whipped heavy cream to chocolate emulsion.
How to Assemble Chocolate Strawberry Mousse Cake
Before assembling the mousse cake, make sure that you have everything ready because the mousse sets fast and should not be set aside.
Pour the chocolate mousse into silicon molds about 2/3.
Place frozen Strawbery Confit into a chocolate mousse and press lightly.
Add more chocolate mousse and cover with the chocolate sponge.
Using a spatula, clean the mousse from the sides of the molds.
Freeze assembled cakes into the freezer for 12-24 hours.
Unmold frozen cakes and cover them with mirror glaze or chocolate velour.
Leave the cakes for at least 2 hours in the fridge to defrost before cutting.
How to Make Chocolate Velour
In a small saucepan add white chocolate and cocoa butter.
Heat the mixture to 40oC (104oF), wait until all melted, and transfer into tall cup.
Add food coloring and emulsify with the emulsion blender.
Stray mousse cakes.
Notes
When you are ready to assemble mousse cake, make sure everything is ready because chocolate mousse sets fast.
Make sure you are using oil-based food coloring for chocolate velour.
This recipe makes eight mini cakes or one large mousse cake.