1. Preheat the oven to 350°F (175°C). Grease a 6-inch cake pan with cooking spray or butter and flour.
2. In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking powder, and salt until well combined.
3. Crack the eggs into the mixture and mix them with a hand mixer or whisk until smooth and well blended. Add in the milk, vegetable oil, and vanilla extract and continue mixing for another minute.
4. Pour the batter into the prepared cake pan and smooth it out with a spatula. Bake for 20-25 minutes or until the top is set but still slightly runny on top.
5. Remove the soufflé cake from the oven and let it cool in the pan for about 5 minutes before carefully transferring it onto a wire rack to cool completely.
6. To serve, slice the soufflé cake into wedges and enjoy with your favorite toppings such as whipped cream or fresh fruit.
### Tips
* Make sure to use high-quality cocoa powder for the best flavor and color.
* Don't overmix the batter or it may become tough and dense.
* If you want a more gooey soufflé cake, you can add in some melted chocolate chips or chopped nuts during the mixing stage.
* For an extra touch of elegance, you can sprinkle some powdered sugar on top of the soufflé cake before serving.