1. Heat oven to 325 degrees. Adjust oven racks to upper- and lower-middle positions. Mix flour, salt, and baking soda together in medium bowl; set aside.

2. Either by hand or with electric mixer, mix butter and sugars until thoroughly blended. Mix in egg, yolk, and vanilla. Add dry ingredients; mix until just combined. Stir in chips.

3. Following illustrations below, form scant 1/4 cup dough into ball. Holding dough ball using fingertips of both hands, pull into two equal halves. Rotate halves ninety degrees and, with jagged surfaces exposed, join halves together at their base, again forming a single cookie, being careful not to smooth dough’s uneven surface. Place formed dough onto one of two parchment paper-lined 20-by-14-inch lipless cookie sheets, about nine dough balls per sheet. Smaller cookie sheets can be used, but fewer cookies can be baked at one time and baking time may need to be adjusted. (Dough can be refrigerated up to 2 days or frozen up to 1 month—shaped or not.)

4. Bake, reversing cookie sheets’ positions halfway through baking, until cookies are light golden brown and outer edges start to harden yet centers are still soft and puffy, 15 to 18 minutes (start checking at 13 minutes). (Frozen dough requires an extra 1 to 2 minutes baking time.) Cool cookies on cookie sheets. Serve or store in airtight container.