Toss together flour, baking soda, cornstarch & salt in bowl and set aside.
In med bowl, whisk melted butter and sugars. Add egg and then egg yolk. Whisk in vanilla. Pour wet ingredients into dry and mix. Dough will be soft, yet thick. Fold in chips and nuts. Cover dough and chill for up to 3 days. Chilling mandatory.
Soften out of frig for 10 minutes. (For carmel - roll into balls, push rolo into center and reshape into ball) Each cookie should be about 3 tablespoons of dough. Only place 8 on sheet at a time.
Bake at 325F degrees at 11-12 minutes. Will look very soft. Cool on cookie sheet for 10 minutes before moving to wire rack to cool.
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