✓ Preheat oven to 350°F / 175°C and position the rack in the middle of the oven

✓ Whisk cocoa powder, flour, baking powder, baking soda, and salt together in a large bowl

✓ In a separate bowl, beat sugar, eggs, milk, oil, and vanilla extract with a handheld mixer on medium speed

✓ Gradually pour the dry mixture into the wet mixture, stirring with a spatula until just combined

✓ Carefully stir in boiling water, the batter will thin dramatically

✓ Fold in chocolate chips if using, distribute evenly without crushing

✓ Cover the bowl with plastic wrap and chill the batter for 20 minutes

✓ Lightly grease a 9‑inch round cake pan and dust with a thin layer of flour

✓ Pour the chilled batter into the prepared pan, smoothing the top with a spatula

✓ Bake for 30–35 minutes, or until a toothpick inserted near the center emerges with a few moist crumbs

✓ Rotate the pan halfway through baking for uniform browning

✓ Remove the pan from the oven and place on a wire rack; allow the cake to cool in the pan for 10 minutes

✓ Run a thin knife around the edge, then invert onto a serving plate

✓ While the cake is still warm, drizzle a thin stream of melted chocolate chips over the top

✓ Allow the glaze to set for 5 minutes, the surface will develop a faint sheen

✓ Slice with a hot, wet knife for clean cuts, each slice should reveal a moist, fudgy interior

✓ Serve immediately or store as directed