Preheat the oven to 325 degrees Fahrenheit and grease a 9 inch baking dish with butter or vegan baking stick. Set aside.
In a large bowl, whisk together the gluten free flour, baking powder and salt. Set aside.
In a small bowl, using a spoon, mix together the cornstarch and the water until it is thin and watery. It will be thick and tacky at first.
In a large bowl of an electric mixer fitted with the paddle attachment, or using a hand held mixer, beat the softened butter or vegan baking stick and the granulated sugar until smooth and creamy. About 2 minutes.
With the mixer on low speed, beat in the cornstarch water mixture and vanilla until combined.
Pour in the milk of choice and beat to combine. It will look chunky and that’s normal.
Slowly add in the flour mixture until just combined. You might see little chunks of butter and that’s ok because when it bakes they will melt and be oh so delicious.
Using a spatula, fold in 1 cup of the chocolate chips.
Using the spatula, spread half the batter into the greased baking dish. Smooth with a butter knife.
Pour 1 cup of chocolate chips on top of the batter and gently press down with your hands.
Spread the rest of the batter on top and smooth again using the butter knife.
Sprinkle the remaining ½ cup of chocolate chips on top and gently press into the batter.
Bake in the center rack of the oven for 60 minutes until the cake is a beautiful golden brown yet still soft and springy when gently touched.
Take out of the oven and keep the cake in the baking dish. Wait at least until the dish cools before serving or you may burn your hand and the cake may fall apart.
For extras, cover the top with foil and leave at room temperature.