The rich, deep flavors of an espresso balance the sweetness of the cookie.
Preheat oven to 160°C/325°F. Mix together peanut butter, brown sugar, sugar, egg, vanilla extract, baking soda, and salt in a large bowl until combined. Stir in chocolate chips.
Scoop dough into equal-sized balls and place on parchment paper-lined baking sheets, spacing balls about 5 cm/2 in. apart. Use fork tines to flatten and make crisscross marks on cookies. Sprinkle with flaky sea salt, if desired.
Bake at 160°C/325°F for approx. 15 min. or until edges are crisp. Cool on baking sheets for 2 min., then transfer cookies to cooling rack to cool completely. Enjoy!
Cook's Tip: Can omit morsels and make flourless peanut butter cookies if desired. Yield will be closer to 20 cookies.