• In a sifter or a medium bowl, combine dry ingredients.
• In a large bowl, beat sugar and butter just until sugar is well incorporated.
• Add the eggs and the single yolk, one at a time, combining after each. Do not beat the batter at this point. 
Overmixing will cause cake-like cookies.
• Stir in vanilla.
• Sift the dry ingredients onto the dough. If you used a bowl to combine them, add the dry ingredients a little at a time as you mix. Mix on medium speed ONLY until combined.
DO NOT overmix. If you overmix, they will collapse when baked. I usually hand-mix the flour using my favorite hand-mixing tool.
• Stir in the chocolate chips by hand.

For Pan Cookies

• Let the tray cool for 5 minutes, then slide the parchment paper with the cookies onto a cooling rack to cool completely (or at least 15 minutes) before cutting.
• Before you bake, preheat your oven to 375 degrees F and let it heat for at least 30 minutes more.
• Spread dough evenly over a parchment-lined baking sheet or 9×13 pan. I use a glass 9×13 pan.
• I put my pan of cookie dough in the freezer for at least an hour. This part is optional, but your cookies will be better if you do it.
• After an hour or two in the freezer, place the frozen cookies in the well-heated oven. 
• Bake until desired doneness. 30-40 minutes. Lower times will make the cookie doughier.

Round, drop cookies

• Drop tablespoons of dough 2″ apart onto a parchment-lined baking sheet.
• I put my pan of cookie dough in the freezer for at least an hour. This part is optional, but your cookies will be better if you do it.
Before you bake, preheat your oven to 375 degrees F and let it heat for at least 30 minutes more.
• After an hour or two in the freezer, place the frozen cookies in the well-heated oven.
• Bake 10-14 minutes. Lower baking times will make the cookies doughier.
• Let cool on the pan for 5 minutes, then slide the parchment paper with the cookies onto a cooling rack to cool completely 
• Let cool completely and store in an airtight container.