I saw this recipe at Helene's renowed blog 
Super Kitchen Machine They were very quick and easy to make and tasted good too.
Here is how I made them:
Ingredients:160g walnuts
Salt
240g Medjool dates, seeds removed 
(I had bought them in Misir Carsisi "The Spice Bazar" when we were in Istanbul)40g unsweetened cocoa powder
1/2 tsp vanilla
For decoration: glace cherries, berries etc.
Preparation:    Put walnuts and a pinch of salt in TM Bowl. Process for 5 seconds on Speed 5
    Add dates and process for 5 seconds on Speed 5. (Use TM Spatula as well if needed)
    Add cocoa and vanilla. Process for another 5 seconds on Speed 5
    Get small pieces and transfer them into mini muffin/cup cake baking sheets. Decorate with cherries. (I obtained 11 brownies in total)
    Cool them for at leats 2 hours in the fridge before you serve
Enjoy...
Photos: http://thermomixtarifdefterim.blogspot.com/2011/12/surprise-brownies.htmland these are Helene's ones: 
http://www.superkitchenmachine.com/2009/1506/raw-food-brownies.html