Preheat the oven to 350°F. Line two sheet pans with parchment paper. Sift the flour, cocoa, salt and baking soda. Set aside.
Cream the butter with both sugars, vanilla and espresso powder. Add the eggs and mix to combine. Add the dry ingredients and mix to combine.
Add the Heath Bar chunks, finish mixing in by hand to avoid breaking up the toffee bits.
Use a #40 scoop (3/4 oz) or tablespoon to scoop the dough into 1.5" balls. Place the cookie balls onto the sheet pan, spacing them 2" apart. At this point some or all of the cookie balls can be frozen to be baked later.
Bake until the tops are lightly puffed and still soft, about 10 minutes. Cool for 5 minutes before transferring to a cooling rack.
Notes
If measuring the flour by volume use the “dip & sweep” method. That is, dip the measuring cup into the flour bin, overfill it, then sweep away the excess.