If your local supermarket doesn't have freshly ground peanut butter, you can grind your own by putting peanuts into a food processor and processing until it looks like peanut butter.

Preheat oven to 325 degrees Fahrenheit.

Put peanut butter, maple syrup, egg, and butter into a mixing bowl, and mix until well blended.

Add cocoa powder and baking soda and mix until it is the consistency of smooth cookie dough.

Butter a 9-inch by 9-inch baking pan and press dough into it.

Bake for 20 to 23 minutes.