Beat the egg in a mixing bowl. )If using a flax egg, mix up your ground flax seed and water in a mixing bowl and let sit for a few minutes so it can gel up).

Add the creamy peanut butter, sugar, baking soda, and salt to the egg and mix until well combined.

Chill the dough for about a half hour.

Preheat the oven to 350 degrees, and line two cookie sheets with parchment paper. Pour a few tablespoons of sugar into a bowl.

Roll the chilled dough into balls that are one inch in diameter, then dip into granulated sugar, Bake at 350 degrees for 12-14 minutes, or until cookies are golden.

When you remove them from the oven, place an unwrapped Hershey's Kiss into the center of each cookie and press it down. Let cool for about 10 minutes on the baking sheet, then transfer to wire racks to cool.