Preheat oven to 325 degrees. Line a cookie sheet with parchment.

1. Melt your butter in a heat-safe mixing bowl.  Note: It doesn’t need to be ALL the way.  See photos for an example- I’ve found the best stage is when about half the butter is liquid, but the rest is super soft.  Like the texture of pudding.  You want it to easily stir completely smooth when you touch it.

2. Mix in brown sugar, white sugar, egg yolk and vanilla.

3. Measure your flour by spooning lightly into your measuring cup and then leveling with a knife.  Sprinkle flour, baking soda, baking powder, and salt on top and then mix together.  Stir in oats and chocolate chips. (Or raisins, if you are using those, instead)

4. Form dough into one large ball and place on prepared baking sheet.  Gently press down to about 3/4 inch thick.  I like to press a few additional chocolate chips into the top of the dough before baking.

5. Note:  All ovens cook differently and baking time will vary depending on how much you press your cookie down.  Set a timer for 10 minutes so you can keep a close watch for the remainder of the baking time.  Bake for 11-14 minutes, until edges are set and center looks set, but still soft.  Let cool for 10-15 minutes before using an extra large spatula to transfer to a cooling rack.