Mix together the egg, brown sugar, peanut butter, butter and vanilla until well-combined.

Add the flour, baking soda and salt and mix just until incorporated.

Fold in the chocolate chips.

Cover bowl and place in fridge for 1-2 hours.

Preheat oven to 350 degrees Fahrenheit.

Scoop out dough and make cookies the size of about two tablespoons. You don't need to roll the dough into balls. Place onto prepared cookie sheet.

Bake for 10-15 minutes or until the edges and tops of cookies are set but centers are still gooey.

Allow to cool for another 10 minutes.