1. Preheat the oven to 325, and line a 9 x 5-inch loaf pan with parchment paper.
2. In a microwave-safe bowl, combine the butter, sugar and cocoa powder.
3. Microwave for 30 seconds on HIGH.
4. Stir, and microwave for another 30 seconds on HIGH.
5. Stir the mixture very well, and then add the salt and vanilla. Stir for 1 minute to cool the mixture.
6. Next, add in the egg, and stir until its incorporated.
7. Finally, add the flour, and stir for 50 strokes!
8. Spread the batter into the prepared pan.
9. Bake for 23 minutes, or until a toothpick inserted comes out with fudge crumbs clinging to it. The surface of the brownies is shiny when done and starting to crack.
10. Let cool completely in the pan, and then lift out using the parchment paper.
11. Chop into 1/2″ cubes when cool. Set aside.
12. Next, make the pudding: whisk together the sugar, cornstarch and salt in the bottom of a 2-quart saucepan. Slowly add the milk and egg yolk while whisking.
13. Turn the heat on the pan, and bring it up to a gentle simmer, while constantly whisking. Be sure to scrape the edges of the pan frequently to prevent lumps. Whisking vigorously will break up any lumps.
14. Remove the pudding from the heat when it thickens (and coats the back of a spoon), and stir in the Irish Cream Liqueur and butter. Stir until melted.
15. In two small dishes, layer the brownie cubes with the pudding. You should get 3 layers (I only did two for photography purposes–more is always better!)
16. Cover the trifles and refrigerate for at least 4 hours, or overnight.
17. Before serving, whip the heavy cream and powdered sugar together in a bowl with a hand mixer on HIGH until soft peaks form.
18. Dollop each trifle with whipped cream, sprinkle with chocolate shavings and serve.