Cream butter and sugars 2-3 min or until light and fluffy. Add eggs, vanilla, and milk; mix well. Whisk dry ingredients together in a small bowl, then add to creamed mixture. Stir until just combined. Refrigerate the dough, well covered, for 48 hrs.
Preheat oven to 350. Form rounded balls of dough about 1 1/2 inches in diameter and bake about 8-9 min. (Remove when edges are beginning to become a little brown, but center does not look done). Keep on cookie sheet 2-3 minutes or until set. Remove and cool on paper towels.
This cookie is flat, but has crisp edges with a soft, gooey center. Fabulous.