- With the rack in the middle position, preheat the oven to 350°F (180°C).
- In a blender, purée all of the ingredients until smooth. Transfer to a pot. Bring to a boil while whisking constantly. Pour into a 10-cup (2.5 litre) soufflé dish. Set aside.
- In a bowl, combine the flour, baking powder and salt.
- In another bowl, cream the butter and sugar with an electric mixer. Add the egg and whisk until smooth. With the machine running on low speed, add the dry ingredients alternating with the milk and vanilla.
- Using an ice cream scoop or a large spoon, drop the batter over the hot sauce in the soufflé dish. Place the dish on a baking sheet.
- Bake for 40 minutes or until a toothpick inserted in the cake comes out clean. Let cool for 15 minutes. Serve warm or cold.