Preheat your oven to 350° degrees Fahrenheit. In a small bowl, mix together the water and ground flaxseed and set aside for 5 minutes to allow it to gel.
Heat the vegan butter in a large bowl in the microwave until it is very soft but not melted. Cream together the butter and sweetener with a whisk until creamy and slightly fluffy. Mix in the milk and vanilla.
Add the almond flour, coconut flour, cocoa powder, baking powder and salt and mix until combined. Fold in the mayo and food coloring until just combined.
Pour the batter into a well-greased 8 inch cast iron pan. Place in the oven and bake for 45-48 minutes. When finished, the outside of the cookie should be firm, and the interior will be springy but still somewhat firm to the touch. It will firm up more as it cools. When you take the pan out of the oven, sprinkle the white chocolate chips on top, gently pressing a few into the top of the cookie.
Once the cookie has cooled a bit, top with your favorite toppings and enjoy!
Notes
The nutrition information is for the cookie only, not optional toppings.
The amount of food coloring you add will depend on the brand you use and how strong they are. For natural food coloring, aim for 30-35 drops.
Nutritional values are estimates only and do not include carbs from sugar alcohols.
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