Preheat oven to 325 F. Line a 8x8 pan with parchment paper and spray with non stick spray.
Melt chocolate and butter together over medium heat in saucepan. Set aside.
Mix eggs, instant espresso, and butter with an electric mixer. Mix until it gets a little thick.
Add in vanilla and Baileys. Mix for a few more minutes.
Pour melted chocolate/butter mixture in, but make sure it's warm, NOT hot.
Add flour and baking soda. Just mix to combine.
Bake for 40-45 minutes, rotating once halfway through.
For the frosting:
Cream butter, salt, Baileys, espresso powder and powdered sugar.
Add in powdered sugar a little at a time to adjust to your preferred sweetness.
Wait for the brownies to cool before frosting.
(I actually preferred cooling the brownies in the fridge after I frosted them to let the frosting harden a bit)
Optional - sprinkle some extra instant espresso powder on top of frosting! YUM
Notes
When it cools it will slump down in the middle. THIS IS NORMAL. Trust me, the end result is worth it. It doesn't need to look pretty to taste good:)
If you put your leftover brownies in the fridge overnight, then just zap them the next day in the microwave for 8-10 seconds and they are perfect. Not too hot, not too cold.
Recipe by You Gotta Eat This! at https://yougottaeatthis.com/featured/2014/03/14/baileys-irish-cream-brownies/