Preheat the oven to 350°F (180°C), spray a 9x13 baking dish with non-stick spray, and line it with parchment paper so that there is an overhang on either side. Set aside.
Sift the all-purpose flour and unsweetened cocoa powder into a bowl, add the salt, and mix together. Set aside.
Add butter to a microwave-safe bowl along with the chocolate chips or chopped chocolate and melt them together in the microwave. It doesn’t take too long to melt, so do it in 30 second increments bringing it out to stir every 30 seconds until melted.
Add the sugar, eggs, and vanilla extract to the melted butter and chocolate and whisk together until well mixed.
Add the wet ingredients to the dry and mix into a thick batter.
Add the sprinkles and fold them in.
Transfer the batter to the prepared 9x13 dish and smooth down.
Place into the oven and bake for 30-35 minutes. You will know the brownies are done when they are dry and shiny on top and when a toothpick inserted into the center comes out with melted chocolate or moist crumbs but NO wet batter.
While the brownies are cooling, prepare your chocolate fudge topping. Melt the butter in a saucepan and then add the sugar and milk.
Stir continuously until it reaches a full boil, then remove from the heat, add the chopped chocolate or chocolate chips, and stir vigorously until they have melted and you have a smooth chocolate sauce.
It will start setting pretty fast, so immediately pour it over the still-warm brownies, sprinkle it with sprinkles and let it cool completely.
Cut into squares and enjoy.