Preheat oven to 350 degrees. Line a 9" cake pan with parchment paper then lightly spray or butter, set aside.
Using a double boiler, melt butter and chocolate, mixing until smooth. Remove from heat, stir in the Nutella and set aside to cool.
In a 1 c. glass measuring cup, dissolve espresso powder in warm water. Add salt and vanilla, set aside.
In the bowl of a stand mixer fitted with the whisk attachment (note: I have two KitchenAid bowls so I used one for the whites and one for the yolks), beat the egg whites until foamy, about 2 minutes. Gradually increase speed to high and slowly add ½ c. sugar, beating until soft peaks form. If you’ve got the ice cream cone top when you lift your whisk out, you’ve gone too far! Set aside.
In the bowl of a stand mixer fitted with a whisk attachment, beat the egg yolks with the remaining ½ c. sugar until the eggs are light and have almost doubled in volume, about 3-4 minutes. Add the cooled chocolate mixture and beat until just combined. Scrape down sides and bottom of bowl and with mixing speed on low, add the coffee mixture. Beat until just combined.
Remove the bowl from the stand and gently fold in 1 c. of the beaten egg whites. After about 30 seconds of gentle folding, add remaining egg whites and continue folding until almost completely combined, do not over mix.
Pour the batter into the prepared pan, gently sprinkle chocolate chips and raspberries over top (they will sink a little) and place in oven to bake for 38 to 40 minutes. The cake will have a semi-crisp top and will still jiggle a bit. Remove from oven and allow to cool to room temperature. The center and edges of the cake will fall a bit- this is normal. Once the cake is cool, cover with plastic wrap and refrigerate for 2 hours. To serve, invert onto a cake stand or platter, dust with cocoa powder and top with fresh whipped cream or a scoop of ice cream.