For the Brownie Cakes:
Preheat the oven for 300 degrees F.
Line 4, 4-inch round cake pans with parchment paper and grease the pans.
In a small bowl, combine the flour, salt, and espresso powder.
In a sauce pan, combine the chocolate, butter, sugar, and cream. Melt over medium-low heat until it's smooth.
Allow the chocolate mixture to cool slightly to room temperature.
Add the eggs, one at at time. Mixing well after each addition.
Add the vanilla, and mix well.
Place the chocolate mixture in a large bowl.
Add the flour, and mix well.
Divide the batter evenly between the pans.
Divide the raspberries evenly. Push the berries into the batter.
Bake for 35 minutes.
Remove from the oven and allow to cool for about 10 minutes.
Turn the cakes out on to a cooling rack and allow them to cool completely.
For the Filling:
While the cakes cool, using an immersion blender, whip the cream for only about 15 seconds.
Add the powdered sugar, and continue to whip for about 15 more seconds. Do NOT over mix or the cream will curdle.
To Assemble the Cakes:
Place one mini-brownie cake on a cake stand. Fill with 1/4 of the cream.
Top with the second brownie cake. Top with 1/4 of the cream.
Dust with cocoa powder.
Repeat with the other two cakes.