Preheat the oven to 350°F (175°C) and grease a 9x13 inch baking pan.
In a large mixing bowl, combine the flour, sugar, cocoa powder, baking powder, and salt.
In a separate bowl, whisk the milk, vegetable oil, and vanilla extract together until smooth.
Gradually add the wet mixture to the dry ingredients, stirring until just combined.
Carefully stir in the boiling water and optional chocolate chips until well combined.
Pour the batter into the prepared pan, spreading it evenly.
Bake for 30-35 minutes, or until a toothpick comes out clean from the edges.
Allow the cake to cool in the pan for about 10 minutes before serving, optionally with ice cream or whipped cream.