I used this recipe
Bake 15 minutes on 180°C(depending on cookie cutter size).
Cool completely on wire racks.
I made the royal icing. Then I separated 1/4 which I colored in black. I thinned the rest of royal icing with some water. You have to value when the consistency is right for piping and flooding all-in-one. The point is, it has to be thin enough to flow, while remaining thick enough that it doesn’t fall off the side of the cookie.
To ice cookies, first outline and fill with white at the same time. I use a nozzle tip 3. Imediatelly I made the black line using a nozzle tip 1.