Place hazelnuts and dates in food processor and pulse for at least 30 seconds so that they are mixed well.
Add in cacao, syrup, vanilla, and cinnamon; pulse.
Spray an 8x8 pan with nonstick spray, or cover with coconut oil, and then pour brownie "batter" into pan and use a spatula to smooth everything out.
Place pan in freezer; allowing it to set.
While brownies are setting, create icing.
Mash avocado with a fork--make sure to mash REALLY well so that mixture is smooth.
Add in cacao, syrup and oil and use an electric mixer to combine everything; stir until smooth.
Pour icing overtop of brownies, using a spatula to smooth everything out and place back in freezer for approximately 5 minutes before cutting into brownies.