Preheat oven to 350 degrees F. Line a 9''X13''inch baking pan with foil, allowing the edges to hang over. Set aside.

Set up a double boiler by placing a bowl on top of a pan of simmering water. The bowl should not touch the water. Place butter and chocolate chips in bowl. Melt butter and chocolate. Stir as needed to ensure even melting.

Once melted, remove from heat and add sugar and brown sugar. Stir to combine.

Add eggs on at a time, making sure each egg is fully incorporated before adding the next. Mix together using a hand mixer, or simply using a sturdy spatula.

In another bowl, whisk together flour, cocoa powder, and salt. Alternate adding dry mixture and Guinness to the batter. Start and end with the dry mixture. Fold in chocolate chips.

Pour batter into prepared pan. Bake for 25-30 minutes until toothpick inserted in center of brownie comes out clean. Let brownie cool in pan while you prepare fudge.

In a medium sauce pan, melt butter. Add brown sugar and corn syrup and stir to combine. Add sweetened condensed milk and heat oven medium-low heat. Do not boil mixture. You just want it to be hot enough for the white chocolate chips to melt.

Add white chocolate chips and pinch of salt. Remove from heat and stir until chips have melted and mixture is smooth. Pour mixture over slightly cooled brownies. Spread into an even layer. Let harden at room temperature or store in the fridge uncovered.

Let fudge set for at least 1 hour (best if let set overnight) before slicing and serving.

If desired, drizzled melted semi-sweet chocolate over set fudge for decor and added garnish.