Process walnuts and cashews in food processor until oils released and nut butter is formed. Place nut butter in a large bowl and combine with sweeteners. Add the baking powder, salt, egg, vanilla extract.
Cut the chocolate into small chunks. Stir chopped chocolate into the dough.
Using spoon or cookie scoop, drop dough balls onto silicon mat lined baking cookie sheet. Flatten each cookie with fingers to desired thickness (very flat can be baked crisper).
Bake for about 8-10 minutes or until cookies are browned to desired crispness. Let cool for 10 minutes, then transfer to rack to cool completely.
Per cookie: 56.1 calories, 5.4g fat, 8.4g carbs with erythritol, 0.7g fiber 6.6g erythritol, 1.1 NET carbs, 1.6g proteinNote 1: 8 ounces of prepared walnut butter can be substituted for nuts.Note 2: Any sweetener equivalent to about 1/2 cup of sugar can be used in place of both sweeteners listed.