Beat cold butter with both sugars until just creamy, about 60 seconds.
Mix in eggs and vanilla on low until combined; do not overbeat.
Add dry ingredients. Blend on low until a thick dough forms.
Fold in chocolate and walnuts until evenly distributed.
Scoop eight large mounds, about 4 ounces each, stacking them tall.
Chill the scooped dough 10 minutes to reduce spread, if kitchen is warm.
Bake 11–13 minutes until tops are set and edges browned; rest 10 minutes.
Notes
Variation: Swap walnuts for pecans, or use half milk chocolate for a sweeter bite. Finish hot cookies with a pinch of flaky salt. Storage: Keep in an airtight container 3 days, or freeze scooped dough and bake from frozen, adding 1–2 minutes.This recipe is an original creation inspired by classic Levain Bakery Cookie Copycat Recipe flavors. All ingredient ratios and instructions are independently developed.