01 - Preheat the oven to 375°F. Line two baking sheets with parchment paper.
02 - In a large bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt.
03 - In a separate bowl, whisk granulated sugar, brown sugar, eggs, milk, sour cream (or yogurt), melted butter, and vanilla extract until smooth and fully blended.
04 - Add wet ingredients to the dry ingredients and gently mix until just combined, avoiding overmixing.
05 - Carefully fold the semisweet chocolate chips into the batter.
06 - Using a large cookie scoop or 1/4 cup measure, drop spoonfuls of batter onto the prepared sheets, spacing each about 2 inches apart.
07 - Bake for 11 to 13 minutes, or until the tops are set and a toothpick inserted in the center comes out with a few moist crumbs.
08 - Let the muffin tops cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.