Line three baking sheets with parchment paper (or silicone mats) and set aside.
In a bowl, combine flour, cocoa powder, cornstarch, salt, baking soda and espresso flakes. Mix well and set aside.
In a mixing bowl, cream butter and sugars together until light and fluffy. Add one egg and mix well. Add peanut butter, vanilla and last egg. Mix until eggs are well incorporated.
While mixing on low speed, slowly begin adding the dry ingredients. Stop and scrape bowl. Add chocolate chunks and butterscotch chips and stir until combined.
Scoop out cookie dough using a cookie scoop (or spoon) and place on a lined baking sheet. Place in fridge for 20-30 minutes.
Preheat oven to 375 degrees (F). Place cookie dough scoops 2" apart on lined baking sheet and bake 10-12 minutes. Remove from oven and allow to cool 10 minutes before transferring to cooling rack. Store in an airtight container for up to 3 days.
* I use one of the lined baking sheets to place all of the scooped cookie dough on and then pop that sheet in the fridge to chill. The other two baking sheets I use to bake them. Bake one cookie sheet at a time.
** I used a small cookie scoop which yielded approximately 4 dozen cookies that'll measure 1.5 -2". If you want a larger cookie, use a medium cookie scoop. If you don't have a cookie scoop, use a spoon to scoop out dough and roll with hands, keeping them same sized.