Put 1 tablespoon of chocolate chips in the bottom of a standard-size mug.
In a small bowl, whisk together the dry ingredients (flour, cocoa powder, sugar, baking powder, and salt) until no lumps remain. Add the oil and milk and stir until smooth.
Pour half the batter into the mug, drop in the remaining chocolate chips and the raspberries, and cover with the remaining batter.
Microwave on high for about 90 seconds. (Note that microwave times may vary). Serve warm.
*This recipe has been modified slightly since it was originally published in 2018 to decrease the flour from 3 to 4 tablespoons, and to add an extra tablespoon of chocolate chips to the raspberry layer. I find these changes make for a moister result.I know many enjoyed the original version, so I wanted to highlight this in case you prefer to make it the old way!