Preheat your oven to 350°F [180°C]. Use your hands to butter the bottom and sides of two 8-in [20-cm] cake pans, then line the bottom of each with a circle of parchment paper. For good measure, butter the parchment paper. Set the pans aside.
In a large bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt.
Add the melted butter, eggs, coffee, buttermilk, and vanilla and whisk until the batter is smooth.
Divide the batter evenly among the prepared cake pans (Use a cup measure to be accurate). Place these two onto a baking sheet for easy removal.
Bake until the cakes are firm to the touch and a toothpick inserted in the centers comes out clean, about 30 minutes. Transfer the cakes, still in their pans, to a wire rack and let them cool completely.
Once cool, use a dinner knife to loosen the edges of the cakes from the pans and invert them onto your work surface (you might need to give the pan a little whack). Peel off and discard the parchment.
TO MAKE THE FROSTING
Meanwhile, bring a small pot of water to a boil and then lower the heat to a simmer. Put the chocolate chips in a large stainless-steel or heatproof glass bowl and set it over the pot (the water should not touch the bowl—if it does, simply pour some out). Stir until the chocolate is melted. (Alternatively, you can melt the chocolate in a microwave in 15-second increments, stirring between increments.)
Combine the maple syrup and harissa paste till smooth.
Remove the chocolate from the heat and let cool down slightly.
Whisk in the sour cream, and then the maple syrup mixture.
The frosting should be smooth and quite silky. Refrigerate the frosting until the cakes have cooled. It will thicken as it cools (a good thing).
Once the cakes are cool, put one on a serving platter upside-down so that the flat side is facing up. Spread the jam over the top. Put the second cake on top of the jam-slathered cake, again flat-side up—this way you get a nice flat top. (If the jam makes the layers slip and slide a bit, use a couple of skewers to hold the layers together while you frost the sides and then remove the skewers to frost the top).
Using a small offset spatula or a dinner knife, spread the frosting all over the sides and top of the cake. There’s no need to be perfect with this; I like it kind of rustic looking. But if you’re more of a type-A person, go ahead and smooth the top and sides (and you could even stick strips of parchment paper under the bottom of the cake before frosting it to keep your serving platter clean). Whatever makes you happy.
Let the cake sit for about 1 hour before serving. There’s something about letting each element get to know the others that serves this cake very well. In fact, I prefer to make it the day before and refrigerate it overnight, and serve it cold. Either way, slice and serve with some fresh raspberries alongside if you’d like.
Note: If you only own a single cake pan, fear not! Simply pour the batter into the pan and bake it until a toothpick tests clean (it will take 10 to 15 minutes longer in the oven than the two separate layers). Once the cake cools completely, use a serrated knife to cut it into two layers. Voilà.
Alternatively, you can make a bit more frosting and use it to fill the middle. Or use both- the raspberry jam and the frosting for a really decadent middle!