1Preheat the oven to 350°. Line two baking sheets with parchment paper.
2Put 5 oz of the butter in a heavy-based saucepan over medium-high heat. Cook, stirring occasionally, for 4 minutes until melted and nutty brown.
3Remove from the heat and cool for 2 minutes. Add the remaining 2 oz butter. Stir until melted. Set aside for 15 minutes to cool.
4Put the sugars, salt, vanilla, egg and egg yolk in the blender. Pour in the cooled butter and secure the lid. MIX for 40 seconds until well combined.
5Add the flour and baking soda to the blender and secure the lid. STIR for 30 seconds, scraping down the side and stopping occasionally to use the tamper to press the ingredients into the blades.
6Add the chocolate chips. STIR for 20 seconds, scraping down the side and stopping occasionally to use the tamper to press the ingredients into the blades. To avoid over mixing use a spatula to incorporate any remaining dry ingredients.
7Roll 2 tablespoons of the dough into balls. Place onto prepared baking sheets, allowing 1 ½-inch between each cookie. Use the back of a spoon to flatten slightly. (Raw rolled cookie dough can be stored in the freezer for up to 2 months. When cooking from frozen, bake for an extra 2-4 minutes).
8Bake for 10-12 minutes, swapping the baking sheets halfway through, until light golden.
9Cool on the baking sheets for 5 minutes to firm before transferring to a wire rack to cool.
10Use the CLEAN program to remove cookie dough residue from the blender.
Tip: Chill the cookies on the trays before baking for 20 minutes for more uniform cookies.