a number of years ago, i tried the following recipe and it is truly the best sugar cookie recipe ever. it is, predictably, from my girl martha.
1 cup unsalted butter
2 cups sugar
2 large eggs
4 and 2/3 cups all-purpose flour (plus more for work surface)
1 teaspoon baking soda
1/2 teaspoon salt
1/4 cup buttermilk
with electric mixer, cream butter and sugar until fluffy. add eggs, one at a time, beating well after each. sift dry ingredients and gradually blend into the sugar/egg mixture, alternating with the buttermilk.
wrap dough in plastic and chill until firm. martha suggests 1 hour to overnight. i generally chill this dough overnight. it also freezes well.
heat oven to 350 degrees. on floured surface, roll dough out to approximately 1/8 inch thick. cut into desired shapes. bake until just golden but not too brown - about 10 minutes.