Gather your mise en place; get together all of the equipment needed for the recipe and gather your ingredients.

Preheat the oven to three hundred twenty-five degrees Fahrenheit. Line one or two baking sheets with parchment paper.

In a medium bowl, combine the flour, baking soda, and salt together. Set aside.

Chop the bittersweet and white chocolate if you are using chocolate bars, otherwise measure the chocolate chips. 

Melt the butter in a small pot and place it in a large mixing bowl to cool slightly.

Measure the brown sugar and granulated sugar into small bowls.

Crack the egg into a separate bowl to check for shells, and separate the second egg to get one yolk.

Measure the vanilla extract.

In the large bowl, combine the melted butter, brown sugar, and granulated sugar. Use an electric mixer or whisk to mix until smooth.

Add the egg, egg yolk, and vanilla extract. Beat until the mixture becomes light and creamy.

Add the sifted flour mixture. Use a This word has been an eternal struggle amongst Growing Chefs staff. Is it a flipper? Is it a mixer? Is it offset? All I can tell you is that it is a cooking utensil with a wide, flat blade that is not sharp.spatula to stir until the dry ingredients are just combined; do not overmix.

Add the bittersweet chocolate and white chocolate. Stir with a firm spoon until evenly mixed through the dough.

Scoop tablespoon-sized portions of dough (or use a small cookie scoop) onto the baking sheet, leaving about two inches of space between each cookie.

Bake for twelve to fifteen minutes, or until the edges are lightly browned.

Cool the cookies on the baking sheet for a few minutes, then transfer them to a cooling rack to cool completely.