Step 1: Prepare the Walnuts
Place whole walnuts in a food processor
Pulse in short bursts (10-15 times)
Grind until consistency resembles fine breadcrumbs or almond meal
Walnuts should pinch together slightly between fingers
Do NOT over-process or they'll turn into walnut butter
Stop before oils are released
Set aside ground walnuts
Step 2: Whip the Egg Whites
Ensure mixing bowl and beaters are completely clean and dry
Add 2 egg whites to the bowl (no trace of yolk)
Beat on medium speed with electric mixer
Continue until whites begin to foam and turn white
Gradually add sugar, 1 tablespoon at a time
Keep beating while adding sugar
Continue beating for 3-5 minutes total
Beat until stiff, glossy peaks form
Peaks should stand straight up when beaters are lifted
Step 3: Fold in Walnuts and Vanilla
Add 1 teaspoon vanilla extract to whipped egg whites
Fold gently to incorporate vanilla
Add all 3 cups ground walnuts at once
Use rubber spatula to fold gently
Cut down through center, sweep along bottom, bring up and over
Rotate bowl a quarter turn and repeat
Continue until walnuts are evenly distributed
Work gently to avoid deflating egg whites
Dough should be thick and sticky but hold together
Step 4: Shape the Cookies
Preheat oven to 350°F (180°C)
Line baking sheet with parchment paper or silicone mat
Use spoon or small cookie scoop (1-1.5 tablespoons)
Drop portions of dough onto prepared sheet
Space cookies about 2 inches apart
Optional: Wet fingers slightly and shape into neater rounds
Dough will be sticky - damp fingers prevent sticking
Step 5: Bake to Perfection
Place baking sheet in center of preheated oven
Bake for 13-15 minutes
Watch carefully during last few minutes
Cookies are done when lightly golden on edges and top
Surface should have slightly cracked appearance
Should feel set when gently touched but still soft
Check at 13 minutes - if golden and set, they're done
If pale and wet, bake 1-2 more minutes
Do not overbake or they'll be too hard and dry
Step 6: Cool and Finish
Remove cookies from oven
Let cool on baking sheet for 5 minutes (crucial step)
Do not move cookies before 5 minutes or they may break
After 5 minutes, transfer to wire cooling rack
Let cool completely
Once cool, place on serving plate
Dust generously with powdered sugar using fine-mesh sieve
Serve and enjoy