In a stand mixer beat butter, sugar, salt, egg and milk. Slowly incorporate flour until dough ball forms. Split into two balls and chill until ready to use.
Heat oven to 375 degrees fahrenheit and roll out dough onto a parchment lined baking sheet using powdered sugar to prevent sticking. Cut out shapes using stencils and save scraps for the next batch. Bake 9 to 11 minutes until edges just begin to brown. Remove from oven and smooth by placing parchment paper over the top of freshly baked cookies and press down flat with a slightly smaller baking sheet. Once cool place on paper towel to absorb any butter before assembling.
Once all your components are ready, assemble using royal icing as the 'glue'. This cookie is very delicate so be gentle. Once assembled and dried, you can paint however you like! I was inspired by early 20th century handcrafted German toys.