Preheat the oven to 350 degrees Fahrenheit. Grease an 8x8 casserole dish with oil.
In a bowl of a stand mixer, combine the 1/3 cup of melted Salted Butter, 1 cup of Granulated Sugar, and 1/4 cup of Cocoa Powder. Mix on a medium speed until fully incorporated.
Add in the 2 Large Eggs, 1 tsp of Kosher Salt, 1 tsp of Vanilla Extract, and 3/4 cup of Flour.
Mix on medium speed to fully incorporated then pour into the 8x8 casserole dish.
Bake for 15-18 minutes or until a toothpick comes out clean.
For the fudge topping:
Towards the end of the bake time for the brownie base, begin making the fudge top.
In a medium saucepan, melt together the 1/4 cup of Salted Butter, 1/4 cup Milk, 1/4 cup of Cocoa Powder and 1 cup of Granulated Sugar.
Bring the mixture to a boil and allow to stay at a boil for just 2 minutes.
Remove from the heat and add in the 1 1/2 cups of Powdered Sugar and 1 tsp of Vanilla Extract. Stirring fully together to create a smooth, slightly thick texture.*
Pour the fudge mixture onto the slightly cooled brownie base, smoothing it out to an even layer.
Allow to cool slightly to set into to place and enjoy!
Notes
*You can always add more powdered sugar if your fudge is not very thick and if it is too thick, add just a splash of milk.