Preheat your oven to 350°F (175°C). Grease the 9x13 inch baking dish with butter or non-stick spray.
In a large mixing bowl, combine the flour, granulated sugar, cocoa powder, baking powder, and salt. Mix well.
Add the melted butter, eggs, vanilla extract, and milk to the dry ingredients. Beat with an electric mixer or whisk until the batter is smooth and well combined.
Stir in the chocolate chips until evenly distributed in the batter.
Pour the batter into the greased baking dish and spread it evenly using a spatula.
Carefully pour the hot water over the batter. Do not stir. This will create a gooey layer at the bottom as it bakes.
Bake for 35-40 minutes, or until the edges are set but the center remains soft and gooey. A toothpick inserted should come out with moist crumbs.
Allow the cake to cool for about 15 minutes before serving, then slice and enjoy.
Serve with vanilla ice cream or whipped cream for an extra special treat.