Preheat the oven to 325ºF and line a large baking sheet with a silicone mat or parchment paper.
In a large bowl, stir together the peanut butter and sweetener until well combined. Stir in the egg. The dough should become thick and similar to cookie dough. See recipe notes if yours stays too goopy.
Roll the dough into scant 1 inch balls and set on the prepared baking sheet. Press down to 1/2 inch thick and use your thumb to create a well in the center of each.
Stir the jam well, and then spoon 1/2 a teaspoon into the well of each cookie.
Bake 12 to 15 minutes, or until the edges of the cookies are just firm to the touch. Remove and let cool completely on the pan.
Peanut Butter and Nutella Cookies
Prepare and form the cookie as directed above but DO NOT ADD the chocolate hazelnut spread.
Bake the cookies 12 to 15 minutes, then remove and let cool completely on the pan. If the wells have puffed up, gently re-form them while the cookies are still warm.
Warm the hazelnut spread gently in a microwave-safe bowl to make it runnier, then spoon about 1/2 teaspoon into the center well of each cookie. Refrigerate 30 minutes to set the centers.
Notes
Natural peanut butter varies tremendously between brands. Many are very oily and goopy which can affect this recipe. If your dough is very soft and you can't roll it easily into balls, try adding coconut flour or peanut flour, 1 tablespoon at a time, until it's more like a proper cookie dough.
Nutrition facts for the Peanut Butter & Nutella Cookies:
Per 2 cookies: Calories = 162; Carbs = 7.6g; Fiber = 3.8g; Fat = 12.4g; Protein = 5.6g