Prepare the Brownie Batter

1. Preheat Oven: Preheat your oven to 350°F (175°C). Grease or line a 9×9-inch baking pan with parchment paper.
2. Mix the Wet Ingredients: In a large bowl, whisk together the melted butter, granulated sugar, and brown sugar until smooth. Add the eggs, one at a time, mixing well after each addition. Stir in the Baileys Irish Cream and vanilla extract.
3. Combine Dry Ingredients: In a separate bowl, sift together the all-purpose flour, cocoa powder, and salt. Gradually fold the dry ingredients into the wet ingredients, mixing until just combined.
4. Add Chocolate Chips: If using, fold in the chocolate chips for added texture and extra chocolatey goodness.
5. Pour the Batter: Pour the brownie batter into the prepared pan, spreading it evenly.

Bake the Brownies

1. Bake: Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs (not wet batter).
2. Cool: Remove the brownies from the oven and allow them to cool in the pan on a wire rack for 10 minutes. Afterward, remove from the pan and let them cool completely on the wire rack.