Preheat oven to 350°F.
Mix together the softened butter, brown sugar substitute, and applesauce until smooth.
In a separate bowl, whisk together all of the dry ingredients.
Combine the wet and dry mixtures, then add the syrup, egg, and vanilla.
Mix until a smooth dough forms.
Fold in the chocolate chunks.
Chill the dough for 10 minutes.
Transfer to a greased 7–9 inch pie pan, filling just below the rim.
Bake for 20–24 minutes, until the edges are set but the center still has a slight jiggle.
Let cool completely before slicing so the crispy top can fully set.
