1. Preheat oven to 350°.
2. Weigh or lightly spoon flour into dry measuring cups; level with a knife. Combine flour and next 6 ingredients (through salt), stirring with a whisk.
3. Combine butter and 1/4 cup sugar in a medium bowl, and beat with a mixer at medium speed until light and fluffy (about 3 minutes). Beat in 3 tablespoons milk, molasses, and vanilla extract. Add flour mixture to butter mixture, and beat on low speed until blended. Shape dough into a 6-inch disk. Cover and chill for 30 minutes.
4. Lightly coat hands with cooking spray. Shape dough into 30 balls (about 2 teaspoons each). Place remaining 1/2 cup sugar in a shallow bowl. Roll dough balls in sugar; place 2 inches apart on baking sheets coated with cooking spray. Flatten balls slightly with the bottom of a glass. Bake at 350° for 12 minutes or until lightly browned. Cool on pans 4 minutes. Remove cookies from pans; cool completely on wire racks.