Combine butter, sugar, eggs and vanilla in a large mixing bowl or stand mixer.
In a separate bowl, whisk together flour and salt.
Combine wet and dry ingredients, mixing until combined.
Roll doll on a lightly floured surface to 1/4 inch thickness. Using a 3-inch round cookie cutter, cut dough.
Flip a muffin tin upside down and place sugar cookie circles on each inverted well, molding around each.
Bake for 10 minutes or until edges are lightly browned. Remove and allow to cool for 5 minutes before gently popping off.
Allow cups to cool completely.
If using the glaze, Combine all glaze ingredients in a small bowl, adding water until a smooth consistency. Dip each sugar cookie cup rim into the glaze and then decorate with desired sprinkles and embellishments.