Step 1

1 In a medium bowl, combine the butter, granulated sugar and brown sugar

Step 2

2 Using an electric hand mixer on low speed, beat the ingredients until light and fluffy but still a bit grainy, about 3 minutes

Step 3

3 (If mixing by hand, you’ll see the sugars just begin to dissolve into the butter as they’re combined, 4 to 5 minutes

Step 4

4 )

Step 5

5 With the mixer running, add the whole egg and beat (or stir) on low until thoroughly incorporated

Step 6

6 Add the yolk and milk and beat (or stir) until thoroughly incorporated

Step 7

7 The batter will begin to look smooth and glossy

Step 8

8 Beat (or stir) in the vanilla extract until combined

Step 9

9 In another medium bowl, whisk together the flour, baking soda and salt and thoroughly combined with a whisk

Step 10

10 Add the flour mixture to the butter and egg mixture and mix on low speed (or stir) just until the flour is incorporated

Step 11

11 Using a silicone spatula, scoop to the bottom of the bowl and gently incorporate any hidden pockets of flour

Step 12

12 Fold in about 10 ounces of the chocolate wafers (you can eyeball this; just be sure to reserve a handful of wafers to top the dough balls)

Step 13

13 Spoon the dough onto parchment paper or plastic wrap and wrap it into a disk or log (whatever will fit best in your refrigerator) and refrigerate overnight

Step 14

14 If baking the same day, use a tablespoon to portion 2 tablespoons (30 grams/1 ounce) of dough per cookie -- you should get 36 -- and refrigerate until thoroughly chilled, at least 1 hour and up to 3 hours

Step 15

15 When ready to bake, place a rack in the upper third of the oven and preheat to 350 degrees

Step 16

16 Line a rimmed baking sheet with parchment paper

Step 17

17 Transfer the chilled dough to the counter

Step 18

18 If the dough was chilled overnight, portion out the cookies as instructed above

Step 19

19 Use your hands to roll each cookie into a ball and place on the prepared cookie sheet

Step 20

20 Allow about 2 inches of space in between each dough ball

Step 21

21 Gently press each dough ball into a thick disk, tuck 2 to 3 chocolate wafer into the top of each dough ball, and sprinkle generously with flaky sea salt, if using

Step 22

22 Bake one sheet at a time, for about 12 minutes, rotating the pan after about 7 minutes; the cookies should be golden brown

Step 23

23 (If you want more crisp edges and deeper color, bake for 1 more minute

Step 24

24 )

Step 25

25 Let the cookies rest on the sheet for 3 minutes, then carefully transfer to a wire rack to cool completely or until warm