To make Genoise cake, heat the oven to 355°F (180°C). Butter and flour the bottom and the sides of the 8-inch (20 cm) round pan (or springform pan). Melt the butter in the microwave and let it cool.

In the heat-proof bowl, place eggs and sugar and beat with a hand whisk a few times. Bring the bowl over a water bath or bain-marie with hot water and whisk the egg mixture until foamy. Warm it to 104°F (40°C): check with a cooking thermometer. If unavailable, the mixture should be warm to the touch.

Bring the bowl to the counter and beat the preparation with an electric hand mixer (you can use a stand mixer with a whisk attachment) for 10 minutes until the ribbon stage. Sift half the flour over the bowl and mix with a rubber spatula from the bottom to the top. Add the remaining flour and gently mix. Mix a few spoonfuls of the batter with the warm melted butter, and add to the principal preparation. Gently mix the batter, making sure it does not deflate. 

Pour the cake batter into the prepared baking dish. Bake in the middle oven rack for 30-35 minutes until golden brown. Check the cake for doneness with a toothpick: it should come out clean after inserting it in the center of the cake. Remove it from the oven and rest for 5-10 minutes. Then turn the pan on a cooling rack, allowing the cake to slide off. Let the cake cool completely. 

To make the sugar syrup, pour water, sugar into a small saucepan and bring to a boil. Remove from the heat, add vanilla extract or strawberry liqueur (optional), and let the syrup cool down. 

To make mascarpone whipped cream, bring the bowl of a stand mixer or a large mixing bowl to the freezer for 10 minutes. Pour the cold heavy cream, add cold mascarpone, and whisk at low speed until soft peaks. Add the caster sugar and continue beating at medium, then high speed. The cream will go through medium peaks until stiff peaks. 

To assemble the cake, cut a few strawberries into half, then into more slices each, and place aside. Adjust a mousse cake ring to a diameter of 8 inches (20 cm) and line it with an acetate strip. Place it on a cake board or a serving plate. 

Use a large serrated knife or a cake leveler to cut the cake into three sponge layers. Place the first cake layer inside the ring and soak the cake with the cold sugar syrup using a pastry brush. Add 1/3 of the mascarpone filling and spread it with a spoon or spatula. Place a handful mix of berries over the cream, sinking them slightly. 

Add the second cake layer and slightly press it to adhear to the cream. Soak it, and fill it with cream and a new layer of berries. Place the third layer of cake and press it slightly. Cover the ring with plastic wrap and refrigerate for 2-3 hours. Cover the bowl with the cream using plastic film and chill until the cake is firmed up. 

Once ready to serve, take the cake and cream from the fridge. Remove the ring and acetate collar. Coat the top and sides of the cake with the remaining cream with the spatula. Sprinkle the cake's sides with toasted flaked almonds. Decorate the top of the cake with the remaining berries, dust with confectioners’ sugar (if desired), and serve.