1. In a large bowl, add sugar, oil, and egg. Whisk to combine well.
2. Take a separate bowl, combine flour, salt, and baking powder in it.
3. Drop dry mixture, and milk into the large bowl with egg, alternatively, a little at a time. Beat well after each addition.
4. Pour vanilla and mix well.
5. Into the pie crust, pour the mixture.
6. In a small bowl, add sugar and cocoa. Pour hot water and vanilla in it. Mix well.
7. Gently pour the chocolate mixture into the pie crust.
8. Preheat the oven for 350 degree F.
9. Pop it in oven, and bake for 45-55 minutes or until toothpick when inserted comes out clean
10. Remove from oven, put it on wire rack and let it cool for 2 hours.
11. Cut into slices and serve it immediately.