Preheat your oven to 350 degrees. Spray a 9 by 13 inch baking dish with cooking spray. Set aside.
In a large bowl, mix together the flour, cocoa powder, and salt. Set aside.
In a medium microwave safe bowl combine the butter and chocolate chips. Microwave at 30 second intervals, stirring in between, until the butter and chocolate are fully melted and smooth.
Whisk the sugar into the butter and chocolate mixture. The mixture will be a little grainy, but should be consistent throughout.
Pour the chocolate mixture into the flour mixture. Stir to combine. The batter will be very thick. Stir in the eggs, vanilla, and finally the baileys..
Spread the batter into the prepared pan. Bake for 30.