1. Preheat oven to 350°F (176°C) and prepare a 9×9 inch cake pan with non-stick baking spray.
2. Add the flour, sugar, cocoa, baking soda, baking powder and salt to a large mixer bowl and combine. Set aside.
3. Add the milk, vegetable oil, vanilla extract and eggs to a medium sized bowl and combine.
4. Add the wet ingredients to the dry ingredients and beat until well combined.
5. Slowly add the hot water to the batter and mix on low speed until well combined. Scrape down the sides of the bowl as needed to make sure everything is well combined.
6. Pour the batter into the prepared cake pan and bake for 20-25 minutes, or until a toothpick comes out with a few moist crumbs.
7. Remove cake from oven and allow to cool completely.
8. When the cake has cooled, prepare the pudding. Add the Baileys and milk to the chocolate pudding powder and stir together as directed on the pudding packaging. Set aside.
9. To make the whipped cream, add all ingredients to a large mixer bowl fitted with the whisk attachment and whip until stiff peaks form.
10. To layer the trifle, cut the cake into pieces. add about half of the cake to the bottom of the trifle dish.
11. Sprinkle 1/4 cup of the mini chocolate chips over the cake pieces.
12. Add about half of the pudding and spread into an even layer.
13. Add about half of the whipped cream and spread into an even layer.
14. Repeat another layer of cake, mini chocolate chips, pudding and whipped cream.
15. Top of the trifle with some additional chocolate chips and some remaining cake crumbs.
16. Store the trifle in the fridge prior to serving. Trifle is best if eaten within 2-3 days.