Preheat your oven to 375°F and line a muffin tin with paper liners. Set aside.

In a medium bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt. Set aside.

In a large bowl, whisk together the brown sugar, eggs, yogurt, milk, oil, and vanilla extract until well combined.

Pour the dry ingredients into the wet mixture, and stir until just combined. Be careful not to overmix. Gently fold in the chocolate chips or chunks.

Spoon the batter into the prepared muffin tin, filling each cup to the top for a fuller muffin top.

Bake in the preheated oven for 15 to 20 minutes, or until a toothpick inserted into the center comes out clean (chocolate from the chips may be visible, but the batter should be set).

Let the muffins cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely or enjoy slightly warm.