Lightly oil sides and bottom of an 8x8 inch square baking pan (glass pan if available).
In a medium saucepan, melt butter over low heat. Add coconut sugar and stir until it's dissolved. Remove from heat and stir in cocoa, just until combined. Add vanilla and eggs, one at a time, and stir to combine.
Add flour, chocolate chips, and walnuts and stir to combine, being careful not to over mix. Once the flour is no longer visible, it's ready to pour in the prepared pan. Spread evenly in pan. If desired, sprinkle a few more walnut pieces on top before baking. Bake for 25 minutes. Remove and cool at least one hour before serving.