Step 1

In one, microwave safe bowl, add in the dark chocolate. In a second, add in the mascarpone.

Step 2

Microwave the chocolate in short 15 second intervals, stirring in between, until melted.

Step 3

Microwave the bowl with the mascarpone in two 10 second intervals until soft, similar to the texture of sour cream.

Step 4

Add the 50 grams of sugar into the bowl with the mascarpone and stir to combine.

Step 5

Pour half of the melted chocolate into the bowl with the mascarpone and stir until fully mixed in. Then add in the remaining chocolate and stir one more time. Set aside.

Step 6

Preheat the oven to 350 F and place a rack in the middle of the oven.

Step 7

In the bowl of a stand mixer, add in the flour, salt, baking powder, baking soda, cocoa powder, and hot cocoa mix. Whisk to combine.

Step 8

Add in the sugar, eggs, butter, sour cream, and vanilla. Use the paddle attachment to mix the batter first on low speed for 10 seconds and then medium high for another 10 seconds until just fully mixed.

Step 9

Scrape the sides and bottom of the bowl.

Step 10

Fully line a 9" metal springform cake pan with parchment paper.

Step 11

Add half of the cake batter into the lined pan and smooth it out. Then add in about 3/4ths of the chocolate mascarpone filling and spread it out into an even layer.

Step 12

Pour in the remaining cake mix, smooth it out. And then dollop the top with the remaining chocolate mascarpone and swirl it into the cake batter.

Step 13

Bake the cake in the preheated oven for 35 minutes. After 35 minutes, rotate the cake 180 degrees and bake for another 30 minutes.

Step 14

When the timer goes off, the outside edges should be set but the center of the cake should still be quite jiggly.

Step 15

Remove the cake from the oven and leave it to cool for 10 minutes before removing the springform.

Step 16

Transfer the cake to whichever plate or stand you want to serve it from.

Step 17

Dust the top with powdered sugar and serve warm with a dollop of whipped cream.

Step 18

In a medium mixing bowl, add in the powdered sugar, vanilla, and cold heavy cream.

Step 19

Use an electric mixer (stand or handheld) with the whisk attachment to whip on medium high speed until medium peaks form.

Step 20

Serve dollops of the cream with each slice of cake and store any extra in a covered bowl in the fridge.