Preheat oven to 325 degrees F. Spray a 10-to-12-inch springform pan with cooking spray, spraying sides and bottom of pan; set aside.
In a medium saucepan, add sweetened condensed milk, semi and bittersweet chocolates, and 1 tablespoon of butter. Stir until chocolate is melted and then remove from heat; set aside.
In a large bowl or in the bowl of a stand mixer fitted with the paddle attachment, beat remaining ½ cup butter with the brown sugar and granulated sugar until fluffy. Add eggs and vanilla and beat well, scraping down the sides of the bowl, as needed. Add the flour and salt and mix until incorporated.
Add the chocolate mixture and mix until combined; fold in the toffee pieces and pour into the prepared springform pan.
Bake for 35 to 40 minutes or until center is set. Remove from oven and let cool completely.
Drizzle salted caramel onto brownie. Top with chopped truffles.
When ice cream has softened, spread it over truffles, filling in any space with ice cream in an even, packed layer. Top with Cool Whip and freeze for at least 4 hours or overnight.
Remove from freezer 15 minutes before serving. Release the pan and run a knife along the edge to help release it some more. Remove ring of pan and cut with a large, sharp knife.