Preheat the oven to 300 F or 150 C and grease a 9 x 9 square pan or line it with parchment paper.
In a large bowl, sift together the whole wheat flour, cocoa powder and salt. Keep aside.
In a blender or processor, add the eggs, vanilla extract, oil, honey (or sugar or a combination of both), milk and yogurt. Blend till smooth and homogenous.
Add the blended wet mix into the dry flour-cocoa mix. Mix until just incorporated. Do not over mix.
Spread the batter into the prepared pan. Tap a few times gently to help the batter become uniform. Bake at 300°F for 25 to 28 minutes.
Try the toothpick test to see if it's done. Unlike cakes, the center might still have wet crumbs, but will continue to cook as it cools. Over cooking will result in dry and chewy brownies.
Cool completely to room temperature in the pan. Could take an hour or more, so be patient! Once cool, lift out the parchment paper and slice into squares.
Dust with icing sugar for a festive appearance.