Preheat oven to 350°F. Line two baking sheets with parchment.
Whisk flour, cocoa, baking soda, salt, and espresso powder in a bowl.
Cream butter, brown sugar, and granulated sugar until fluffy, about 2 minutes.
Beat in eggs one at a time, then mix in vanilla until smooth.
Add dry ingredients to the bowl and mix on low just until combined.
Fold in chocolate chips and chocolate chunks until evenly distributed.
Scoop 1½-tablespoon mounds onto sheets, spacing about 2 inches apart.
Bake 10–12 minutes, until edges set but centers still look soft.
Cool on the sheet 5 minutes, then move cookies to a rack to finish cooling.
Notes
For a nutty twist, fold in 1/2 cup chopped toasted walnuts. Prefer extra fudgy? Chill the dough 30 minutes before baking. Store cookies airtight at room temperature up to 4 days, or freeze baked cookies or dough scoops for up to 2 months.This recipe is an original creation inspired by classic Double Chocolate Chip Cookies flavors. All ingredient ratios and instructions are independently developed.