Preheat oven to 350 degrees and line 8x8" baking pan with parchment paper.
Process all brownie ingredients, except chocolate chips, in food processor until smooth.
Stir in chocolate chips.
Spread brownie mixture into baking pan.
Bake for 30 minutes.
Remove from oven and allow to cool completely.
Press down on brownies using parchment paper to flatten them out.
Whisk together topping ingredients, except walnuts.
Spread evenly onto brownies with spatula.
Top with walnuts.
Refrigerate for 1 hour before slicing.