Preheat the oven to 175 C. In a medium bowl, mix 2/3 cup butter, sugar, flour and mix well until it is crisp. Put the finished mixture in a mold and smooth. Bake for 20 minutes.
In a saucepan, mix 1/2 cup butter, brown sugar, corn syrup, and condensed milk. Bring to a boil. Continue to boil for 5 minutes. Remove from heat and beat vigorously with a wooden spoon for 3 minutes. Pour the baked crust with finished caramel and let it harden.
Melt the chocolate in a water bath. Pour caramel over chocolate and evenly smooth. Cool and cut into small squares.