Melt the butter in a saucepan. Add the brown sugar to the butter allowing sugar to dissolve slightly from the heat. Pour into a mixing bowl and let cool to lukewarm. You can also do this all in one microwave-safe mixing bowl. Just melt the butter, stir in the sugar, then heat briefly again in the microwave (about 20 seconds). Let cool in the bowl.
Stir in the vanilla, salt, baking soda, baking powder, espresso powder (if using), syrup and vinegar. Add the eggs, beating well after each. Add flour, stirring to combine, and then mix in the chips.
The dough will be too soft to scoop at this point.
Cover dough and chill overnight or for at least a few hours. Overnight gives better results as the wheat absorbs more moisture.
Preheat the oven to 375 degrees F. Line 2 baking sheets with parchment or Silpat.
Drop the dough by rounded tablespoonfuls onto the prepared baking sheets. Bake the cookies (reversing the pans midway through, top to bottom, bottom to top...if you are baking more than one sheet at a time) until they are just beginning to brown around the edges, 12 to 13 minutes. Remove from oven and allow to cool completely on the pan. Remove with spatula.
Note: If your cookies are browning too quickly at 375F, try lowering the heat to 350F.