In a large bowl, cream together the butter and sugar until light and fluffy.
Mix in vanilla extract, then gradually add flour and salt until combined.
If the dough is too crumbly, add milk a teaspoon at a time until it comes together.
Form dough into a disk, wrap in plastic, and chill for 30-60 minutes.
Preheat oven to 325°F (165°C) and line baking sheet with parchment paper.
Roll out dough to ¼-inch thick and cut into shapes using cookie cutters.
Place cookies on baking sheet, brush tops with egg white, and gently press edible flowers on top.
Sprinkle with sugar and bake for 12-15 minutes or until edges are just golden.
Cool on baking sheet for a few minutes before transferring to a wire rack to cool completely.