Preheat your oven to 350°F (175°C) and grease a 9x9 inch baking pan or line it with parchment paper.
In a medium bowl, whisk together the whole wheat flour, cocoa powder, baking powder, and salt until fully combined.
In a separate large bowl, mix the Greek yogurt, honey (or maple syrup), melted coconut oil, eggs, and vanilla extract until smooth.
Gradually add the dry ingredient mixture to the wet mixture, stirring just until combined. Be careful not to over-mix.
If you're using chocolate chips, fold them into the batter gently.
Pour the brownie batter into the prepared baking pan and smooth the top with a spatula. If desired, sprinkle chopped walnuts or pecans on top for added crunch.
Bake in the preheated oven for about 20-25 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs (not wet).
Allow the brownies to cool in the pan for at least 10 minutes before cutting them into squares.
Notes
Serve on a rustic wooden board with a sprinkle of cocoa powder or powdered sugar.