1-First Step: Gather all ingredients and chill butter, eggs in the fridge. Line baking sheets with parchment paper. Preheat oven to 400°F (204°C) later. This mise en place keeps things smooth for busy schedules.

2-Second Step: Cube 1 cup cold unsalted butter into a large bowl. Add 1 cup light brown sugar and ½ cup granulated sugar. Beat with a hand mixer on medium for 2 minutes until fluffy and light. Cold butter creams slowly, building structure for thick levain cookies. Scrape sides often.

3-Third Step: Crack in 2 cold large eggs one at a time, beating well after each. Mix in 1 tsp vanilla extract until smooth, about 1 minute. Wet mix should look creamy; avoid overbeating to keep dough tender.

4-Fourth Step: Whisk 2½ cups cake flour, 1 tsp cornstarch, ¾ tsp baking soda, and ¾ tsp salt in a separate bowl. Fold dry into wet using a spatula or low-speed mixer. Stop when just combined; lumps are fine. This prevents tough bakery cookies.

5-Fifth Step: Gently fold in 2½ cups semi-sweet chocolate chips and chunks. Use hands if needed. Dough will be thick. For vegan, ensure plant substitutes here.

6-Sixth Step: Scoop 4 oz dough balls (about ½ cup or golf ball plus half) using a scale or cookie scoop. Roll lightly; space 3-4 inches apart on sheets, 3-4 per tray. Refrigerate balls 30 minutes minimum or overnight for best flavor. Chilling is crucial for gooey centers in this copycat recipe. Gluten-free? Chill longer.

7-Seventh Step: Bake at 400°F for 9-11 minutes. Edges turn golden, centers stay pale and soft. Rotate trays halfway. Ovens vary, so check at 9 minutes. High heat sets outsides fast while keeping insides molten, just like Levain Bakery Chocolate Chip Crush Cookies.

8-Final Step: Cool on sheet 10-15 minutes; they firm up. Transfer to rack. Enjoy warm for peak texture. Smaller 2 oz balls bake 8-10 minutes at 375°F. Store as noted below. Adapt for low-cal by baking slightly longer for crispier results.