Brown Sugar Shortbread Cookies

Ingredients
3/4 pound (3 sticks) unsalted butter, at room temperature

1 cup light brown sugar, lightly packed 
2 teaspoons pure vanilla extract 
3 cups all-purpose flour 
1 teaspoon salt​​​
Picture
Steps
  1. ​Preheat the oven to 350° F.  Grease cookie sheets or line with parchment paper. 
  2. Mix butter, sugar, and vanilla on medium speed.
  3. Turn mixer to low speed and slowly add in the salt and flour a little at a time.  Mix until combined, but not too much.
  4. Roll tablespoon-sized pieces of dough into balls and place on prepared cookie sheets. 
  5. Grease the bottom of a glass and press each ball into a round cookie.
  6. Bake for about 15 minutes, checking to make sure they aren’t burning.  Cookies should be golden brown around the edges. 
  7. Leave on cookie sheets a few minutes to cool, then transfer to racks.