In a separate bowl, beat the browned butter, brown sugar and granulated sugar with an electric mixer for 2 minutes. Add in the eggs and best for another 2 minutes until light in color. Add in the vanilla and beat for 30 seconds. Add in the flour and fold it in using a rubber spatula. Add in about 3/4 of the chopped toffee chocolate bars and fold in until evenly distributed.
Gently spoon the blondie batter on top of the partially baked brownie batter without breaking the brownie layer underneath. Sprinkle the rest of the chopped chocolate on top. Bake for 20-30 minutes or until the top layer begins to lightly brown and a toothpick inserted into the center comes out clean.