Position an oven rack in the middle and preheat the oven to 350F (176C).
Grease a 9-inch loaf pan with butter or line with parchment paper, leaving some of the paper hanging out opposite sides like handles. Set aside.
In a small saucepan, bring Guinness beer to a boil. Boil for 5 minutes, until reduced by half (you should have ⅔ cup reduced syrup). Set aside to cool.
In a small bowl mix flour with cacao and baking soda. Set aside.
In a large mixing bowl, whisk coconut sugar, with eggs and vanilla extract.
Add melted butter, Guinness syrup, and Greek yogurt. Whisk to combine.
Stir in dry ingredients. Keep stirring until the mixture is smooth and glossy. Use the whisk.
Mix in cacao nibs or dark chocolate chips (if using).
Pour the mixture into a prepared loaf pan. Bake for 45-50 minutes until a toothpick inserted into the center comes out clean. Be careful not to overbake the cake!
Take the pan out of the oven. Let it cool slightly.
Take the cake out of the pan and place it on a wire rack to cool completely.
Slice and serve.
As a measure, I used a US cup (240ml). Makes 12 slices that serve 12 people.Substitutions
You can substitute whole grain Spelt flour with any whole grain flour. Or use plain/all-purpose flour if you prefer.
You can substitute butter with coconut oil.
You can substitute Grek yogurt with plain yogurt or sour cream.
Substitute Guinness beer with or any other stout beer.
You can substitute cacao nibs with dark chocolate chips. Aim for 75%-85% dark chocolate.
Storing Counter: Once the cake is completely cooled, place it under the cake dome or in an airtight container and keep it on the counter for up to 3 – 4 days. Refrigerator: Cake will keep in the refrigerator for up to a week, in an airtight container. To freeze: Place the sliced cake in an airtight container or zip-lock freezer bag. Keep in the freezer for up to 3 months. Thaw on room temperature.