Preheat your oven to 350°F (175°C). In a mixing bowl, whisk together 3 eggs and ½ cup of sugar for about 10 minutes until pale and thick.

Gently fold in ½ cup of flour until just combined to maintain aerated structure. Pour batter into a greased 9-inch round cake pan and bake for 25-30 minutes.

Remove the cake from the oven and let it cool for 10 minutes in the pan, then transfer to a cooling rack until completely cooled. Slice into two even layers.

Prepare a soaking mixture of boiling milk or sugar-water, and drizzle it over each cake layer.

In a large bowl, combine 2 lbs of sour cream, 1 ½ cups of sugar, and 15 oz of sweetened condensed milk. Mix with a hand mixer until fluffy and smooth.

In a small saucepan, heat ½ cup of milk and dissolve 4 packets of Knox gelatin in it. Once dissolved, incorporate this into the mousse mixture.

Place one layer of the soaked cake in a springform pan. Spoon half of the mousse filling over the first layer.

Place second layer on top and pour remaining mousse over it. Cover with plastic wrap and refrigerate for 3-4 hours.

In a small saucepan, heat 1 cup of heavy cream until simmering. Remove from heat and add 1 cup of semi-sweet chocolate chips and 1 stick of unsalted butter.

Stir until the chocolate and butter melt completely and create a silky smooth ganache.

Once the mousse has set, gently release the cake from the springform pan. Pour warm ganache over the top.

Allow ganache to cool before refrigerating the cake again for an hour.