Position an oven rack in the center of the oven and preheat to 350 degrees F.

Grease an 8 x 8-inch baking dish, then line it with parchment paper, allowing the paper to overhang two sides of the dish.

In a bowl, with a hand mixer, blend the peanut butter, honey, egg, baking soda, and 3 tablespoons of coconut (if using) until thick and creamy.

Scoop the batter into the baking dish and use a rubber spatula to spread the batter until it is even.

Bake the bar for 18 to 20 minutes, or until set and the edges are just barely starting to brown (the center will be slightly lower that the edges when set).

This batter has a tendency to overbake very quickly, so be sure to check for doneness at around 18 minutes.

Remove the bar from the oven, sprinkle on the remaining coconut for garnish, and allow to cool fully in the pan before cutting.