Preheat your oven to 350°F (175°C) and line a 10x15 inch baking pan with parchment paper.

In a medium bowl, whisk together the flour, cocoa powder, baking powder, and salt.

In a large bowl, beat the eggs until thick and lemon-colored. Gradually add the sugar and vanilla, beating well.

Gently fold the dry ingredients into the egg mixture until just combined.

Spread the batter evenly into the prepared pan and bake for 12-15 minutes, or until the cake springs back when lightly touched.

Allow the cake to cool in the pan for 5 minutes, then turn it out onto a clean kitchen towel sprinkled with cocoa powder.

Roll the cake up in the towel and let it cool completely.

To make the filling, heat 1/2 cup of heavy cream until just simmering and pour over 4 ounces of chopped dark chocolate. Let sit for a few minutes, then stir until smooth. Allow to cool to room temperature.

Unroll the cake and spread the chocolate filling evenly over the surface. Roll the cake back up without the towel.

For the glaze, heat the remaining 1/2 cup of heavy cream and pour over the chopped semi-sweet chocolate. Stir until smooth, let cool slightly, then pour over the cake.

Let the glaze set before serving. Slice and enjoy your Triple Chocolate Roll Cake!