Finely chop up the chocolate and set it aside.
Add the eggs and sugar to a medium sized saucepan. Set the mixture over medium heat, and vigourously whisk the mixture until it reaches a temperature of 170℉ / 76℃.
Remove the mixture from the heat, and immediately stir in the chocolate. Stir until the mixture is cohesive, then set it aside to cool for at least 20 minutes.
In the meantime, whip up the whipped cream. Add the heavy whipping cream to a medium sized mixing bowl. Beat the mixture with a hand or stand mixer until it reaches stiff peaks. Set aside in the fridge.
Add the butter and salt to a medium sized mixing bowl. With a hand or stand mixer, beat the butter and salt for 3-4 minutes, until it's light and fluffy.
With the mixer running, start adding in big dollops of the chocolate egg mixture, mixing until combined before adding in the next. Once all of the chocolate has been incorporated, beat the mixture for an additional 2-3 minutes, until light and fluffy.
Add in the whipped cream and very gently fold it into the chocolate mixture.
Once the cake has cooled to room temperature, slice a thin layer off of the top of the cake to make it a flat layer.
Line the springform pan you baked the cake in with plastic wrap or parchment paper. Set the cake back into the pan, then top it with the french silk pie filling.
Cover the cake with plastic wrap and set it in the fridge for at least two hours to allow time for the pie filling to set up. Once you're ready to serve the cake, make the whipped cream.