Preheat oven to 350°F. Line a sheet pan or two with parchment paper. In the bowl of a stand mixer fitted with a paddle attachment, beat the butter and sugar on medium high speed until light and creamy, about 4 minutes.
Add the eggs one at a time, mixing after each. Add the vanilla.
In a separate bowl, sift together the flour, cocoa powder, baking soda, and salt. Add to the mixer and mix until just combined. Add the white chocolate chips or chunks.
Scoop by the rounded tablespoon (use a medium 1½ Tbsp cookie scoop or large 3 Tbsp cookie scoop) onto the prepared sheet pan. Bake until edges are crisp, about 8-9 minutes (or 10-12 minutes for large cookies). Let cool on the pan for a few minutes, then transfer to a wire rack to cool completely. Repeat with remaining cookie dough. Let cookie sheet pan cool in between batched (which is why it's helpful to have 2).
Store the cookies in an airtight container at room temperature for several days.
Calories: 189kcal, Carbohydrates: 26g, Protein: 3g, Fat: 9g, Saturated Fat: 5g, Cholesterol: 30mg, Sodium: 108mg, Potassium: 76mg, Fiber: 1g, Sugar: 17g, Vitamin A: 199IU, Vitamin C: 1mg, Calcium: 23mg, Iron: 1mg