Preheat the oven to 350°F/180°C
Line two baking cookie sheets with parchment paper
In a bowl mix together the flour, baking soda, and salt
In a mixing machine with a paddle attachment or a mixing blender,
add the butter and sugar and cream them together on medium until smooth
Add the egg and mix until well blended
Add the egg yolk and vanilla and continue to mix until well combined.
Scrape and clean the sides of the bowl with spatula
with the mixing machine or blender on slow speed, gradually add the flour mixture until just combined ans incorporated
Add the semi chocolate chips and and mix on slow speed until well blended throughout the cookie batter
Wrap cookie dough in plastic and refrigerate for at least 1 hour before scooping
Scoop individual portions using a small or medium size ice cream scoop or tablespoon and place cookie dough balls onto lined cookie pan spacing them apart about 1 1/2 inch
Bake for 10-12 minutes until lightly golden
Once baked transfer cookies to wire rack and cook completely
Store in air tight jar or container for up to 2 weeks