1. Preheat the oven to 350º F, and make sure the baking rack is in the center of the oven.
2. Spray a 9-inch square baking dish with oil. Place parchment paper on the bottom of the dish with a couple of extra inches on the sides.
3. In a large mixing bowl, sift together the flour, cocoa powder, baking powder, and salt. Set aside.
4. In a small pot, combine the milk, yogurt, and sugar.
5. Heat over low heat, stirring regularly, until hot but not bubbling or simmering.
6. Stir until the sugar is dissolved and the mixture is a bit glossy.
7. Turn off the heat, and add the chopped chocolate, stirring until the chocolate has melted and the mixture is smooth.
8. Add the oil and vanilla powder, and stir to combine. (If mixing in chocolate chips for rocky road brownies, set aside and allow the mixture to cool for 15 to 20 minutes so they won’t melt. Otherwise, skip ahead.)
9. Once the melted chocolate mixture has cooled to lukewarm, add the wet ingredients into the dry, and mix with a wooden spoon until combined. (If making rocky road brownies, add most of the chopped walnuts, chocolate chips, and vegan marshmallows, reserving a little of each to sprinkle on top.) Gently fold them into the batter.
10. Spread the batter into the prepared baking dish.
11. Sprinkle on the reserved nuts, chocolate chips, and a marshmallow or two. Gently press marshmallows into the top of the batter.
12. Bake the brownies for 30 to 35 minutes or until a tester comes out with moist crumbs but no wet batter. (If baking plain brownies without the add-ins, bake for 5 minutes less, or 25 to 30 minutes.)
13. Remove the finished brownies from the oven and let them cool. Enjoy!
