- With the rack in the middle position, preheat the oven to 160 °C (325 °F). Line two baking sheets with parchment paper.
- In a bowl, combine the flour, baking soda, and salt. Set aside.
- In another bowl, combine the melted butter, brown sugar, egg yolks, and vanilla with a wooden spoon, until the mixture is well blended. Stir in the dry ingredients and chocolate chips.
- With a spoon, drop 30 ml (2 tablespoons) of dough per cookie onto the baking sheets, leaving 5-cm (2-inch) between each cookie. Flatten lightly with your fingers.
- Bake for 11 to 12 minutes (the centre of the cookie will still be soft but will firm up as they cool). Let cool on the baking sheet for a few minutes then transfer to a cooling rack. Bake the remaining dough the same way.
- Store the cookies for a few days in an airtight container.
For a denser cookie with a crackled finish; bake the cookies for about 8 minutes. Remove from the oven and drop the baking sheet a couple of times on a work surface to flatten the cookies. Put them back in the oven for 2 to 3 minutes to finish baking.
To keep the cookies soft, add a slice of fresh bread or a slice of apple to the container.