Preheat oven to 350°. Line 13 x 9-inch baking dish with aluminum foil, letting the sides overhang; spray with cooking spray.
Prepare Brownie: In small sauce pot, heat stout to boiling; reduce heat to medium-low and simmer 5 minutes or until reduced to about a cup. Remove from heat; cool.
In large bowl, with mixer on medium-low speed, beat sugar and butter 3 minutes or until light and fluffy. Add eggs, 1 at a time, scraping sides of bowl with rubber spatula after each addition. Add chocolate syrup, vanilla extract and stout; beat until combined. Add flour and salt; beat just until combined. Pour batter into prepared dish.
Bake 30 minutes or until toothpick inserted in center of brownie comes out clean; cool in pan on wire rack 30 minutes. Refrigerate brownie at least 1 hour or overnight.
Prepare Cream Filling: In large bowl, with mixer on low speed, beat powdered sugar and butter 3 minutes or until light and fluffy, scraping sides occasionally; turn off mixer. Add Irish cream; beat on low speed 2 minutes or until smooth. Evenly spread filling over surface of brownie; refrigerate while preparing glaze.
Prepare Chocolate Glaze: In large bowl, add chocolate morsels and whiskey. In small saucepot, heat butter and corn syrup to boiling over medium heat; pour over chocolate mixture and let stand 2 minutes. Whisk chocolate mixture until smooth; evenly spread glaze over surface of filling layer.
- Refrigerate at least 2 hours or overnight. Use foil to lift brownie out of dish. Cut brownie lengthwise into 4 strips, then cut each crosswise into 6 bars.
