1-Preheat your oven to 350°F (175°C) and prepare an 8- or 9-inch springform pan by lining the bottom with parchment paper and lightly greasing the sides.

2-In a large bowl, sift together the dry ingredients: all-purpose flour, cocoa powder, baking powder, baking soda, granulated sugar, and salt. Whisk to combine.

3-In a separate bowl, whisk together the wet ingredients: large eggs, sunflower oil, full fat sour cream, and vanilla extract until well blended.

4-Gradually pour the wet ingredients into the dry ingredients, mixing until just combined. Be careful not to overmix.

5-Slowly add the hot water (just off the boil) to the batter, whisking constantly until a smooth, liquid batter forms. The hot water helps to activate the leavening agents and dissolve the sugar for a moist cake.

6-Pour the batter into the prepared springform pan and smooth the surface with a spatula.

7-Bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean with a few moist crumbs attached.

8-Cool the cake completely on a wire rack, then carefully trim the top to level it using a serrated knife. Place it back into the springform pan.

9-Chop the dark chocolate (55-60% cocoa solids) into small, even pieces for even melting.

10-Heat half of the heavy whipping cream with honey or corn syrup in a saucepan until it just begins to simmer.

11-Pour the hot cream over the chopped chocolate and let it stand for 2 minutes to allow the chocolate to melt.

12-Whisk gently until the mixture is smooth and glossy. Set aside to cool to room temperature.

13-In a separate bowl, whip the remaining heavy whipping cream with cocoa powder until it reaches soft peaks. Be careful not to overwhip, as this can cause the cream to become grainy.

14-Fold the whipped cream into the cooled chocolate mixture in two stages: first, add about a third of the whipped cream and fold to lighten the chocolate mixture, then add the remaining cream and fold until evenly combined.

15-Spread the truffle mixture evenly over the cooled cake in the springform pan.

16-For the glaze, chop additional dark chocolate and place it in a heatproof bowl.

17-Heat heavy whipping cream with honey or light corn syrup in a small saucepan until just simmering.

18-Pour the hot cream over the chocolate and let it stand for 2 minutes.

19-Whisk until the mixture is smooth and shiny. Allow it to cool slightly until it thickens to a pourable consistency.

20-Carefully pour the glaze over the chilled cake and spread it evenly with an offset spatula.

21-Chill the cake until the glaze sets (about 30 minutes).