In a medium bowl, whisk together all dry ingredients (except sugar substitute) until well combined, set aside.
In a separate bowl - the bowl of a stand mixer fixed with a paddle attachment, or a large bowl, if using a hand mixer - cream butter and sugar until smooth and fluffy. Be sure to scrape down the sides of the bowl a few times, to make sure everything is incorporated into the mix. Add egg and vanilla, continue beating until egg is fully incorporated and mixture is once again smooth and fluffy.
With mixer turned down to low speed, slowly add dry ingredients mix to the mixing bowl of wet ingredients, and carefully mix until well incorporated and smooth.
Wrap dough ball in plastic film, chill for 1 hour. This is an important step for any gluten free cookie dough, don’t skip it!
Line 2 cookie sheets with parchment paper.
In a small bowl, mix pecans, brown sugar substitute and spices. Add in heavy cream and vanilla, mix until well combined.
Roll cookie dough into balls that are about 1.5" in diameter, and place them on cookie sheets – leave about 2" between the cookies.
Gently use your thumb to press down in the middle of each cookie, making an indentation. Roll thumb slightly to stretch the indentation out a little.
Fill each indentation with about a teaspoon of pecan filling, then chill the pans for another 30 minutes before baking.
Preheat oven to 350 F (180 C).
Bake for 10-12 minutes, until lightly browned.
Allow to cool on sheets for 5 minutes or so, before gently transferring to baking rack or counter to finish cooling.
Once completely cool store in an airtight container until serving.