In a heat safe bowl, melt the chocolate, butter and espresso powder in the microwave at 30 second intervals or over a double boiler on the stove.
Once that is melted, set aside.
In a separate bowl, whip the heavy cream with an electric mixer until it slightly thickens.
Sift in the powdered sugar and cocoa powder together over the heavy cream.
Blend together until combined.
Add the vanilla extract and use the hand mixer to combine and mix until a chocolate whipped cream has formed with medium soft peaks.
Transfer the whipped heavy cream mixture into the melted chocolate bowl and fold the two together to create the dark chocolate mousse.
Fill a piping bag with the dark chocolate mousse.
Prepare your trifle glasses, jars, or cups to be filled.
Layer with crumbled brownie first, then pipe a layer of the dark chocolate mousse, then add a layer of whipped cream.
Repeat this process until you reach the top of your trifle container, ending on whipped cream.
For an added garnish, sprinkle with espresso powder and add a bite size piece of brownie to the top.
Enjoy!