Preheat the oven to 350 degrees. Grease the bottom of a 13X9” baking pan.
Place the unwrapped caramels in a medium saucepan along with the evaporated milk. Heat over medium to low heat until the caramels have melted completely, stirring occasionally.
While the caramels are melting, make the brownie mix according to the package directions.
Pour ½ of the brownie mix into your prepared pan, spreading it evenly.
Bake for 8-10 minutes until the batter has set.
Remove the brownies from the oven and sprinkle evenly with the chocolate chips. Let sit for 1-2 minutes until the chips are melted and can be spread over the brownie layer.
Pour the melted caramel over the chocolate layer and gently spread it out over the chocolate layer.
Spoon the remaining brownie mix carefully over the caramel layer and spread to the edges.
Place the brownies back in the oven and cook until done, about 20-22 minutes.
Let cool completely before cutting.
Make the chocolate sauce
Melt the butter and chocolate together in a small saucepan.
Add the water, sugar, and salt. Bring the sauce to a full boil, stirring until the sugar is incorporated.
If you are making the chocolate sauce ahead, let the sauce boil, without stirring, for at least ten minutes. When you reheat the sauce, bring it back to a full boil and boil for 2-3 minutes more.
If you are using the sauce immediately, boil the sauce without stirring for 15 minutes.
Assemble the Sundae
Place a brownie in the center of a small plate or bowl. Top with vanilla ice cream and pour chocolate sauce on top.