Turn on the oven to preheat to 350 F (180 C) and line a baking sheet with parchment paper. Blend butter and sunflower butter together in a stand mixer until you have a lump-free mixture. Mix both powdered erythritol and brown sugar erythritol into the mixer.
Add vanilla extract and almond milk to the stand mixer and blend it in until you have a fluffy and creamy mixture. In a separate bowl, combine almond flour and baking soda. Add the dry ingredients to the stand mixer and blend together.
Scoop 2-tablespoon portions of cookie dough onto the parchment paper. The original recipe will make 10-12 cookies, depending on how thick your dough is. Use the back of a fork to press the portions of dough down into flat cookies with a little design in the centers.
Bake the cookies for 14-18 minutes. Check for browned, firm edges with softer middles. The cookies need to cool entirely before you lift them from the baking sheet.