Whisk together flour blend, baking soda and salt to aerate and combine; set aside.

Beat butter with electric mixer on medium-high speed in a large bowl until creamy. Add brown sugar and sugar and beat until lightened, about 3 minutes, scraping down bowl as needed. Beat in vanilla, then beat in eggs one at a time allowing each one to be incorporated before adding the next. Beat in the dry mixture until a few streaks of flour remain. Add chocolate (and nuts, if using) and beat just until combined. Cover the bowl and chill for at least 4 hours but preferably overnight.

Position racks in upper and lower thirds of oven. Preheat oven to 375°F/190° Line two baking sheets with parchment paper.

Form golf ball sized balls and place the cookies 8 per pan, spaced evenly apart. No need to press them down.

Bake for about 9 to 12 minutes or until lightly browned with the edges firmer than the centers, which should be soft. The cookies firm up tremendously upon cooling. Cool cookies completely on pans set on racks. (Make subsequent batches with cooled pans). Cookies are best served the same day but may be stored at room temperature in an airtight container for up to 3 days.