Pre-heat the oven to 350F.

Whisk all the dry ingredients in a bowl. In a separate bowl, whisk egg with sugar. Add milk, oil and warm water to that and give a whisk. Pour the dry ingredients to wet ingredients bowl and give it a mix. Pour it in a 6-inch round baking pan and bake for 25 minutes.

Once the cake is cooled completely, crumble it and keep it aside.

Whisk egg yolks with sugar until it's smooth.

In a saucepan, pour cream and bring it almost boil. Add butterscotch chips and stir until it's all mixed together. Add vanilla extract to the saucepan.

Now, pour ½ cup of the butterscotch cream mixture to the egg mixture, whisking at the same time. Next pour the egg mixture back to the saucepan containing the butterscotch mixture and give it a stir. Put it back on stove and let it simmer for 5 minutes or until it looks thick like custard.

Once done, let it cool completely at room temperature, and then refrigerate it overnight.

Finally churn it in the ice cream machine along with the chocolate cake crumble.