Heat the oven to 350°F and line a baking sheet with parchment paper.
Whisk the flour, ginger, cinnamon, and baking soda in a bowl.
In a second bowl, beat the butter and brown sugar until smooth. Add the molasses, egg yolk, and vanilla and mix well.
Stir in black food coloring until the mixture turns deep black. Add the dry ingredients and stir until a dough forms.
Roll the dough between two sheets of parchment to 1/4-inch thickness. Cut out cat shapes and place them on the baking sheet.
Bake for 8 to 10 minutes until the edges look set. Cool completely on the sheet.
Mix the powdered sugar and milk to form a thick icing. Use a small amount to attach two candy eyes to each cookie.