Step 1

1 Make the cookies: Position a rack in the middle of the oven and preheat to 350 degrees

Step 2

2 Spread all the walnuts (for the cookies and topping) on a baking sheet and toast for 10 to 12 minutes, shaking the pan every now and then, until the walnuts are fragrant and slightly darkened

Step 3

3 Remove the walnuts to a plate to prevent overcooking

Step 4

4 Once cool enough to handle, finely chop

Step 5

5 In the bowl of a stand mixer fitted with the paddle attachment, or using a large bowl and a hand mixer, beat the butter and granulated sugar on medium speed until light and fluffy, scraping the bowl as needed, 2 to 3 minutes

Step 6

6 Add the egg yolks and beat on medium speed until the yolks are incorporated, scraping the bowl a few times, about 2 minutes

Step 7

7 Add about two-thirds (75 grams) of the walnuts, along with the flour and salt, and beat on low speed until the batter clumps together into a few large pieces

Step 8

8 Remove the dough from the bowl, shape into a thick disk and wrap in plastic wrap

Step 9

9 Refrigerate for at least 1 hour, or up to 3 days, until firm

Step 10

10 Return the oven to 350 degrees, if you turned it off after toasting the nuts

Step 11

11 Line 2 large, rimmed baking sheets with parchment paper

Step 12

12 Remove the dough from the refrigerator and break off pieces, forming them into balls just smaller than a golf ball

Step 13

13 Each piece should weigh about 35 grams — you can also make them smaller, if you like

Step 14

14 Place the balls onto the lined baking sheets, spacing them a couple of inches apart and refrigerate for 10 minutes

Step 15

15 (If you only have room in the refrigerator for one pan, you can chill the second while the first batch is baking

Step 16

16 )

Step 17

17 Make the topping: In a small bowl, combine the remaining walnuts with the brown sugar, coconut, butter and five-spice powder

Step 18

18 Take the shaped cookies out of the fridge and brush them with the beaten egg

Step 19

19 Bake for 5 minutes, then remove from the oven and create a thumbprint in each cookie

Step 20

20 Fill the thumbprint with about 1 teaspoon of walnut streusel topping and return to the oven for 15 to 18 minutes, rotating from front to back halfway through, until lightly golden

Step 21

21 Let the cookies cool on the sheet for a few minutes and then transfer to a wire rack to cool completely

Step 22

22 Repeat with the second batch (you may have a little streusel left over depending on the yield and how big your thumbprints are)

Step 23

23 VARIATIONS: This cookie is easily amended to be gluten-free and vegan

Step 24

24 Use gluten-free all-purpose flour, vegan butter and flax eggs, and brush with oat milk rather than an egg wash

Step 25

25 This results in a cookie with more of a crunch

Step 26

26 For the flax eggs, combine 2 tablespoons of ground flax seeds with 5 tablespoons of water

Step 27

27 If you want to simplify this recipe, you can simply add a whole walnut to the center, in place of the crumble