Preheat the oven to 350F and gather all ingredients.

In a mixing bowl, add the softened butter and peanut butter.

Add heavy cream and mix thoroughly.

Add flax seed and coconut flour. You can add additional spices here, if you'd like to have a different flavor.

Mix the batter well until it becomes a bit thick and dough-like.

Add the baking soda, baking powder, and erythritol and stir in very well. As you stir vigorously, the residual heat from the friction will start to warm the peanut butter.

Add egg to the mixture.

Continue mixing very well until you get a creamy, but still pliable, mixture.

Roll your cookie dough into balls and place them on a cookie sheet. Make sure they are spread apart at least 1 inch on each side.

Press each cookie down with your hand and then lightly trace a pattern on the top (if you'd like). I used a meat mallet to impart the pattern on mine. A fork pressed (lightly) horizontally, then diagonally, will give the traditional pattern.

Bake them for 15 minutes. You want semi-crisp edges here. When you take them out of the oven they will feel extremely soft to the touch, but you need to let them cool completely. Once they come back to room temperature, they will start to harden up a little bit, so they can be moved around easily. As they are cooling, sprinkle the top with erythritol.