3. Add both sugars and beat on high 1-2 minutes. Add eggs and vanilla. Beat until fully incorporated.

4. Switch to a paddle attachment.  (3)Add the chocolate chips (if using) and mix gently. 

5. Add the flour mixture and mix until (4)just incorporated. 

6. Touch test the dough.  It should feel slightly sticky, but not much should stick to your finger.  If it is very sticky add flour 2T (.5 oz) at a time.  If it is firm or dry, you have added too much flour and I don’t know a good way to reverse this.

7. Using your (6)hands, roll the dough into balls 1.5 inches tall (for bigger cookies see instructions below).  Place on an ungreased cookie sheet 3 inches apart. 

8. Cover and refrigerate 30 minutes or until firm.  You can hold the dough up to two days in the refrigerator or up to 6 months in the (7)freezer.

9. (8)15-20 minutes before baking, position the oven rack to the second highest setting. Preheat the oven to 375. 

10. Remove the dough from the refrigerator and bake (9)8-10 minutes.  They are ready to come out of the oven when they are domed and puffy, show few signs of browning and look a bit underdone. 

11. Leave the cookies on the cookie sheet for (10)2 minutes.  Remove them to a cooling rack so they will cool evenly.  Wait ten minutes, then serve your Perfect Peanut Butter Cookie!

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Notes
1.  Mixing the flour allows the final dough to have an even distribution of ingredients without over-mixing it.

2.  Beating the butter and shortening gives the dough a better rise in the oven, making the cookies lighter. Butter is good for taste and shortening is good to make the cookie softer.

3.  Adding the chocolate chips before adding the flour evenly distributes them without overmixing the final dough.  Do not over-mix or it will discolor the dough. 

4.  Just incorporated is the point when you no longer see white spots of flour.  Do not overmix! Over-mixing will ruin the cookies.  They will bake flatter and look greasy.  See the problem section for a picture of a very over-mixed cookie. 

5.  You will be able to tell at this point if you have the fat/flour ratio right.
not enough flour- it will stick to your hands when shaping it, forms a messy looking ball
just right- won't stick to your hands, but just barely, forms a smooth ball
too much flour- dough has to be forced into a ball, crumbly dough, rough looking ball

6.  The same problems occur when over-handling the dough as over-mixing it.  They will bake flat and look greasy.  Handle the dough as little as possible while still shaping them properly.
 
7.   To freeze, place the dough balls on a plate or baking sheet side by side cover and freeze at least an hour.  You can then bag them and they won’t be stuck together when you take them out.

8.  It takes most ovens much longer to preheat than when the oven tells you it’s ready.  I have an oven thermometer which is very helpful.  When my oven beeps telling me it’s ready, it’s usually 50-100 degrees too low.  It will ruin your cookies to bake them at the incorrect temperature.  My oven is also calibrated incorrectly.  I have to turn it to 385 degrees for it to actually be 375 degrees.

9.  Determining when they are done:
underdone- the are tall, shiny in the middle, pale in color, fall apart when transfered from the cookie sheet, fall through on the cooling rack
perfect- domed, puffy, show a few signs of browning, look a bit underdone but are not shiny on the top, hold together during transfer
overdone- flat, many brown spots, may break when transfering, hard and crispy when cooled
If they cook faster than 8 minutes the oven is too hot or the cookies are too small.  If they take longer than 10 minutes the oven is too cool or the cookies are too big.

10.  It is important to wait this 2 minutes.  They continue to cook from the heat of the sheet without being over-cooked in the oven.  Also, they will hold together better and be less likely to fall in the middle if you wait.