In a large mixing bowl, combine gluten-free flour, cocoa powder, baking soda, and sugar. Whisk until well mixed. Add plant-based milk, vegetable oil, and vanilla extract. Mix until smooth and homogeneous. Pour into a greased 9-inch springform pan and bake at 350°F for about 20 minutes.

Once the cake is done baking, let it sit in the pan for 10 minutes before transferring it to a wire rack to cool completely.

Whip vegan heavy cream until soft peaks form. Fold in melted vegan chocolate chips until combined.

Spread the prepared vegan chocolate mousse evenly over the top of the cooled cake. Chill in the refrigerator for at least 3 hours.

Heat vegan heavy cream in a saucepan until simmering. Pour over vegan chocolate chips in a bowl, let sit, then stir until smooth. Pour ganache over the mousse layer.

Chill the cake in the refrigerator for an additional 30 minutes before serving.