1. In a bowl, mix together the flour, spices, baking soda and salt. Set aside.
2. Using a stand mixer, whisk together the coconut oil, molasses and brown sugar. Add the egg and egg yolk (leave out the egg yolk if you are using white flour) and whisk again. Incorporate dry ingredients with the paddle attachment of your mixer, or with a wooden spoon, and mix until a homogenous and smooth dough is obtained.
3. Form the dough into two balls, wrap each one with plastic and refrigerate for 30 minutes.
4. Meanwhile, mix together all ingredients for the icing. Fill an icing bag and set aside.
5. Preheat oven to 375°F.
6. Take the dough out of the refrigerator and transfer to a floured work surface. Using a rolling pin, roll out the dough until 1/2 cm thick and cut out your cookies with your favourite cookie cutters.
7. Place the cookies on a baking sheet lined with parchment paper and bake for 8 to 10 minutes. Let cool completely and decorate with the icing.