I used two different color doughs to make this zebra pattern.
These cookies are crisp to taste,but not that fragile as usual butter cookies, because I added water and High-gluten flour to increase their tenacity.

Step 1: The Ingredients

Coco Dough

30g High-gluten flour(bread flour)
90g Low-gluten flour(Pastry flour)
40g butter
20g coco powder
10g suger powder
25g full egg
15ml golden rum(or water)

White Dough

30g High-gluten flour(bread flour)
90g Low-gluten flour(Pastry flour)
40g butter
30g suger powder
25g full egg
15ml white rum or Cointreau(or water)

Yield: about 100 cookies.

Step 2: Make Dough

Cream butter and sugar.Add egg, rum and coco powder,stir to combine.
Add flour and stir，make them to a coco dough.
Make the white dough as the same way.

Step 3: Make Zebra Pattern Log

Press doughs to two pancake and put one overlay the other, press them gently but not evenly，or your zebra pattern will be too neat.
Cut them to 2 pieces.
Don't like the usual cookie dough, you will find the dough is a little elastic and hard to cut off ,it's all right ,because we used high-gluten flour and rum(water).
Put one part overlay the other,press again,make a parallel cut ,and stake up again, and again......
Repeat 4~6 times(depend on what resolution you want.)
Roll the dough to a log.