Preheat the oven to 350F and line two baking sheets with parchment paper.
In light saucepan heat butter over medium heat to brown it, stirring constantly until the butter begins to foam and turns a golden brown. It should emit a nutty aroma.
In a large mixing bowl, combine the cooled brown butter, brown sugar, and white sugar. Whisk until combined. Add the egg, egg yolk, and vanilla.
Next pour the flour, baking soda and salt, folding until just combined . Carefully fold in the chocolate and toffee pieces.
Scoop the cookies into balls and places 2 inches apart on the baking sheet.
Cook for 10 -12 minutes or until the edges are golden brown and the center is a bit gooey.
