Preheat oven to 350F/175C.
Butter the sides of a 9-inch springform pan. Line the base with parchment paper. Do NOT skip this step or your chocolate torte will stick and be difficult to plate.
In a small saucepan, mix the berries, butter and cream. Bring the mixture to a simmer over low/medium heat. Simmer softly for about 15 minutes, or until the mixture smells slightly of berries. Stir constantly to avoid scorching.
Remove the pan from the heat and strain the berries from the cream mixture. Save the elderberries for our Elderberry Granola Bars linked in the article. Or, compost the berries.
Use the whisk attachment of your mixer to beat the sugar, salt and eggs on high speed. Mix until it becomes very thick and pale. The mixture will be thick and silky.
Use the double boiler over low heat to combine the cream mixture and the chocolate. Stir as the mixture melts until it has completely done so - it will look glossy. Remove from the heat once melted.
Add a bit of the chocolate mixture to the egg mixture to temper the eggs and prevent them from "scrambling" in your torte. Fold the rest of the chocolate mixture into the egg mixture in 1/3 increments. Do NOT over-mix but continue to fold until evenly combined.
Pour the mixture into the springform pan and bake for 35-40 minutes. Bake until the gloss disappears from the torte top and only the center jiggles slightly when gently moved. It will set up once cooled. Do NOT overbake.
To plate the chocolate torte, allow to cool for at least 30 minutes. Run a knife gently around the inside of the pan walls. Remove the outer ring with caution. If your torte is completely cool and you're confident it's solid, you may run a knife underneath the torte and remove it from the pan bottom. Or you may leave it on the pan bottom and put it on your favorite cake stand.
Dust with cocoa before serving. You may also whip cream and place a dollop on individual pieces of torte, dusting with cocoa afterwards.